bit-manipulation

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LeetCode 3158 - Find the XOR of Numbers Which Appear Twice

LeetCode Problem 3158 Difficulty: 🟢 Easy Topics: Array, Hash Table, Bit Manipulation Solution Problem Understanding This problem asks us to find all numbers in the array that appear exactly twice and compute the bitwise XOR of those numbers. The input is an integer array nums . The problem guarantees that every value appears either once or twice, never more than twice. Our task is not to count how many duplicate...

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LeetCode 3670 - Maximum Product of Two Integers With No Common Bits

LeetCode Problem 3670 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Bit Manipulation Solution Problem Understanding We the objective is to maximize the product rather than count pairs.

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LeetCode 3621 - Number of Integers With Popcount-Depth Equal to K I

LeetCode Problem 3621 Difficulty: 🔴 Hard Topics: Math, Dynamic Programming, Bit Manipulation, Combinatorics Solution Problem Understanding This problem asks us to count integers x in the range [1, n] such that the popcount-depth of x is exactly k . The popcount-depth is defined via a sequence p0, p1, ... where p0 = x and pi+1 = popcount(pi) for all i ≥ 0 . The popcount of a number is the...

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LeetCode 3615 - Longest Palindromic Path in Graph

LeetCode Problem 3615 Difficulty: 🔴 Hard Topics: String, Dynamic Programming, Bit Manipulation, Graph Theory, Bitmask Solution Problem Understanding We are given an undirected graph with n ≤ 14 vertices. Each vertex has a character label. We may choose any simple path in the graph, meaning a sequence of adjacent vertices in which no vertex is visited more than once. If the labels encountered along that path form a palindrome, the...

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LeetCode 3644 - Maximum K to Sort a Permutation

LeetCode Problem 3644 Difficulty: 🟡 Medium Topics: Array, Bit Manipulation Solution

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LeetCode 3882 - Minimum XOR Path in a Grid

LeetCode Problem 3882 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Bit Manipulation, Matrix Solution LeetCode 3882 - Minimum XOR Path in a Grid Problem Understanding We are given an m × n grid of integers. Starting from the top-left cell (0, 0) , we must reach the bottom-right cell (m - 1, n - 1) by moving only right or down. For every path, we compute its cost as the...

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LeetCode 3878 - Count Good Subarrays

LeetCode Problem 3878 Difficulty: 🔴 Hard Topics: Array, Stack, Bit Manipulation, Monotonic Stack Solution LeetCode 3878 - Count Good Subarrays Problem Understanding We are given an integer array nums , and we must count how many subarrays are good . A subarray is considered good if the bitwise OR of all elements in that subarray is equal to at least one element that appears inside the same subarray. Suppose a...

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LeetCode 3877 - Minimum Removals to Achieve Target XOR

LeetCode Problem 3877 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Bit Manipulation Solution LeetCode 3877 - Minimum Removals to Achieve Target XOR Problem Understanding We are given an array nums and a target value target . We may remove any subset of elements from the array, including removing none of them or even removing all of them. After performing the removals, the remaining elements form a new array. The bitwise...

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LeetCode 3858 - Minimum Bitwise OR From Grid

LeetCode Problem 3858 Difficulty: 🟡 Medium Topics: Array, Greedy, Bit Manipulation, Matrix Solution LeetCode 3858 - Minimum Bitwise OR From Grid Problem Understanding We are given an m x n grid of positive integers. From each row, we must choose exactly one value. After making one choice per row, we compute the bitwise OR of all selected values. Our goal is to make that final OR value as small as...

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LeetCode 3766 - Minimum Operations to Make Binary Palindrome

LeetCode Problem 3766 Difficulty: 🟡 Medium Topics: Array, Two Pointers, Binary Search, Bit Manipulation Solution Problem Understanding This problem asks us to find the minimum number of increment or decrement operations needed to convert each number in a list into a binary palindrome . A binary palindrome is a number whose binary representation reads the same forwards and backwards once leading zeros are removed. For example, the number 5 in...

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LeetCode 3757 - Number of Effective Subsequences

LeetCode Problem 3757 Difficulty: 🔴 Hard Topics: Array, Math, Dynamic Programming, Bit Manipulation, Combinatorics Solution Here’s a complete, detailed technical guide for LeetCode 3757 - Number of Effective Subsequences , following your formatting instructions exactly. Problem Understanding The problem gives us an array of integers, nums , and asks us to determine the number of effective subsequences . The strength of the array is defined as the bitwise OR of...

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LeetCode 3845 - Maximum Subarray XOR with Bounded Range

LeetCode Problem 3845 Difficulty: 🔴 Hard Topics: Array, Bit Manipulation, Trie, Queue, Sliding Window, Prefix Sum, Monotonic Queue Solution Problem Understanding The problem asks us to find a subarray of a given non-negative integer array nums such that the difference between the maximum and minimum elements of the subarray does not exceed a given integer k . Once such a subarray is chosen, we compute the XOR of all its...

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LeetCode 3750 - Minimum Number of Flips to Reverse Binary String

LeetCode Problem 3750 Difficulty: 🟢 Easy Topics: Math, Two Pointers, String, Bit Manipulation Solution Problem Understanding The problem gives us a positive integer n , and asks us to work with its binary representation. First, we convert n into a binary string s without leading zeros. Then, we compute the reverse of that binary string. Our goal is to determine the minimum number of bit flips required so that s...

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LeetCode 3827 - Count Monobit Integers

LeetCode Problem 3827 Difficulty: 🟢 Easy Topics: Bit Manipulation, Enumeration Solution Problem Understanding The problem asks us to count Monobit integers from 0 to n . A Monobit integer is one where all bits in its binary representation are the same. This means there are only two possibilities for a valid Monobit integer: all zeros or all ones. For instance, 0 ( 0b0 ), 1 ( 0b1 ), 3 (...

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LeetCode 3825 - Longest Strictly Increasing Subsequence With Non-Zero Bitwise AND

LeetCode Problem 3825 Difficulty: 🟡 Medium Topics: Array, Binary Search, Bit Manipulation, Enumeration Solution Problem Understanding This problem asks us to find the longest strictly increasing subsequence (LIS) in a given integer array nums , with the additional constraint that the bitwise AND of all elements in the subsequence must be non-zero . In simpler terms, among all sequences you can extract from nums where each number is strictly larger...

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LeetCode 3821 - Find Nth Smallest Integer With K One Bits

LeetCode Problem 3821 Difficulty: 🔴 Hard Topics: Math, Bit Manipulation, Combinatorics Solution Problem Understanding This problem asks us to find the nth smallest positive integer whose binary representation contains exactly k ones . In other words, we are working with numbers that, when written in binary, have a specific number of bits set to 1 . The input consists of two integers: n representing the ordinal position in the sequence...

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LeetCode 3811 - Number of Alternating XOR Partitions

LeetCode Problem 3811 Difficulty: 🟡 Medium Topics: Array, Hash Table, Dynamic Programming, Bit Manipulation Solution LeetCode 3811 - Number of Alternating XOR Partitions Problem Understanding We are given an array nums and two distinct target XOR values, target1 and target2 . A partition divides the array into contiguous, non-empty blocks. Every element must belong to exactly one block, and the blocks must cover the entire array. The partition is considered...

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LeetCode 3806 - Maximum Bitwise AND After Increment Operations

LeetCode Problem 3806 Difficulty: 🔴 Hard Topics: Array, Greedy, Bit Manipulation, Sorting Solution Problem Understanding The problem asks us to find the maximum possible bitwise AND of any subset of size m from an array nums after performing up to k increment operations . Each operation allows us to increase any element in the array by 1. The output is the largest integer that can be obtained as the bitwise...

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LeetCode 3702 - Longest Subsequence With Non-Zero Bitwise XOR

LeetCode Problem 3702 Difficulty: 🟡 Medium Topics: Array, Bit Manipulation Solution Problem Understanding We are given an integer array nums , and we must determine the maximum possible length of a subsequence whose bitwise XOR is not equal to zero . A subsequence is formed by deleting zero or more elements from the array while preserving the relative order of the remaining elements. Unlike subarrays, subsequences do not need to...

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LeetCode 3801 - Minimum Cost to Merge Sorted Lists

LeetCode Problem 3801 Difficulty: 🔴 Hard Topics: Array, Two Pointers, Binary Search, Dynamic Programming, Bit Manipulation Solution Problem Understanding We are given between 2 and 12 sorted lists. At any moment we may choose any two existing lists and merge them. If the two lists are $a$ and $b$, the merge cost is $$\operatorname{len}(a)+\operatorname{len}(b)+ \left|\operatorname{median}(a)-\operatorname{median}(b)\right|.$$ After the merge, the two lists disappear and are replaced by their sorted union. The...

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LeetCode 3755 - Find Maximum Balanced XOR Subarray Length

LeetCode Problem 3755 Difficulty: 🟡 Medium Topics: Array, Hash Table, Bit Manipulation, Prefix Sum Solution LeetCode 3755 - Find Maximum Balanced XOR Subarray Length Problem Understanding This problem asks us to find the longest contiguous subarray that simultaneously satisfies two independent conditions: The bitwise XOR of all elements in the subarray is equal to 0 . The subarray contains an equal number of even and odd elements. We are given...

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LeetCode 3681 - Maximum XOR of Subsequences

LeetCode Problem 3681 Difficulty: 🔴 Hard Topics: Array, Math, Greedy, Bit Manipulation Solution LeetCode 3681 - Maximum XOR of Subsequences Problem Understanding The problem gives us an array nums of non-negative integers. We must choose two subsequences: The first subsequence has XOR value X . The second subsequence has XOR value Y . The two subsequences: May be empty. Must preserve the original order of elements, as all subsequences do....

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LeetCode 3568 - Minimum Moves to Clean the Classroom

LeetCode Problem 3568 Difficulty: 🟡 Medium Topics: Array, Hash Table, Bit Manipulation, Breadth-First Search, Matrix Solution Problem Understanding The problem asks us to compute the minimum number of moves a student must make to collect all litter 'L' in a classroom represented as an m x n grid. The student starts at 'S' with a finite energy that decreases by 1 with each step. Cells 'R' allow the student to...

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LeetCode 3595 - Once Twice

LeetCode Problem 3595 Difficulty: 🟡 Medium Topics: Array, Bit Manipulation Solution Problem Understanding The problem provides an integer array nums where every element appears exactly three times , except for one element that appears once and one element that appears twice . We are asked to identify these two unique elements and return them as a list, with the element appearing once first and the element appearing twice second. The...

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LeetCode 3566 - Partition Array into Two Equal Product Subsets

LeetCode Problem 3566 Difficulty: 🟡 Medium Topics: Array, Bit Manipulation, Recursion, Enumeration Solution Here’s a detailed technical solution guide for LeetCode 3566 following your formatting rules: Problem Understanding The problem asks us to determine whether a given array of distinct positive integers can be split into two non-empty, disjoint subsets , such that the product of the elements in each subset equals a given target value . Each element of...

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LeetCode 3539 - Find Sum of Array Product of Magical Sequences

LeetCode Problem 3539 Difficulty: 🔴 Hard Topics: Array, Math, Dynamic Programming, Bit Manipulation, Combinatorics, Bitmask Solution Problem Understanding This problem asks us to compute the sum of array products for all magical sequences of a given length. A magical sequence is defined as a sequence of indices into the input array nums of length m , such that when you sum 2 raised to each element of the sequence, the...

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LeetCode 3534 - Path Existence Queries in a Graph II

LeetCode Problem 3534 Difficulty: 🔴 Hard Topics: Array, Two Pointers, Binary Search, Dynamic Programming, Greedy, Bit Manipulation, Graph Theory, Sorting Solution Problem Understanding This problem asks us to compute the shortest path between nodes in an implicit undirected graph defined by a nums array and a maxDiff . Each node i corresponds to nums[i] . There is an edge between nodes i and j if the absolute difference of their...

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LeetCode 3495 - Minimum Operations to Make Array Elements Zero

LeetCode Problem 3495 Difficulty: 🔴 Hard Topics: Array, Math, Bit Manipulation Solution Problem Understanding The problem presents a sequence of queries, each defining a contiguous array of integers nums from l to r inclusive. For each array, we are allowed to perform an operation repeatedly: select any two integers a and b and replace them with floor(a / 4) and floor(b / 4) . The goal is to determine the...

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LeetCode 3688 - Bitwise OR of Even Numbers in an Array

LeetCode Problem 3688 Difficulty: 🟢 Easy Topics: Array, Bit Manipulation, Simulation Solution Problem Understanding This problem asks us to compute the bitwise OR of all even numbers in a given integer array nums . A number is considered even if it is divisible by 2, meaning its least significant bit is 0. The task is to iterate through the array, select only the even numbers, and combine them using the...

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LeetCode 3677 - Count Binary Palindromic Numbers

LeetCode Problem 3677 Difficulty: 🔴 Hard Topics: Math, Bit Manipulation Solution Problem Understanding We are given a non-negative integer n and asked to count how many integers k in the range [0, n] have a binary representation that is a palindrome when written without leading zeros. A binary palindrome means that if you take the binary string of a number and read it from left to right or right to...

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LeetCode 3674 - Minimum Operations to Equalize Array

LeetCode Problem 3674 Difficulty: 🟢 Easy Topics: Array, Bit Manipulation, Brainteaser Solution Let's go step by step and produce a fully detailed, reference-style solution guide for LeetCode 3674 following your requested formatting. Problem Understanding The problem asks us to make all elements of an integer array nums equal using the minimum number of operations. Each operation consists of selecting a contiguous subarray and replacing every element in that subarray with...

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LeetCode 3646 - Next Special Palindrome Number

LeetCode Problem 3646 Difficulty: 🔴 Hard Topics: Backtracking, Bit Manipulation Solution Problem Understanding This problem asks us to construct a number system under two simultaneous constraints and then perform a “next greater element” query over that constrained set. We are given an integer n , and we must find the smallest integer strictly greater than n such that the number satisfies a special structural property. A number is considered special...

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LeetCode 3632 - Subarrays with XOR at Least K

LeetCode Problem 3632 Difficulty: 🔴 Hard Topics: Array, Bit Manipulation, Trie, Prefix Sum Solution Problem Understanding This problem asks us to count the number of contiguous subarrays of a given array nums such that the bitwise XOR of all elements in the subarray is greater than or equal to a given integer k . The input array nums consists of positive integers, and k is a non-negative integer. A contiguous...

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LeetCode 3630 - Partition Array for Maximum XOR and AND

LeetCode Problem 3630 Difficulty: 🔴 Hard Topics: Array, Math, Greedy, Bit Manipulation, Enumeration Solution Problem Understanding The problem asks us to partition an integer array nums into three subsequences A , B , and C such that every element belongs to exactly one subsequence. The goal is to maximize the sum XOR(A) + AND(B) + XOR(C) , where XOR and AND represent the bitwise XOR and AND of the elements...

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LeetCode 3599 - Partition Array to Minimize XOR

LeetCode Problem 3599 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Bit Manipulation, Prefix Sum Solution Problem Understanding This problem asks us to partition an array of integers, nums , into exactly k non-empty contiguous subarrays, and then compute the bitwise XOR of each subarray. The goal is to minimize the maximum XOR among these subarrays. Essentially, we are trying to distribute the elements into k groups such that the "largest...

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LeetCode 3594 - Minimum Time to Transport All Individuals

LeetCode Problem 3594 Difficulty: 🔴 Hard Topics: Array, Bit Manipulation, Graph Theory, Heap (Priority Queue), Shortest Path, Bitmask Solution Problem Understanding This problem is a shortest-path optimization over a highly constrained state space where you are repeatedly moving groups of people across a river using a single boat. The twist is that the travel time is not fixed: it depends both on the slowest person in the group and on...

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LeetCode 3585 - Find Weighted Median Node in Tree

LeetCode Problem 3585 Difficulty: 🔴 Hard Topics: Array, Binary Search, Dynamic Programming, Bit Manipulation, Tree, Depth-First Search Solution Problem Understanding We are given a weighted tree with n nodes. A tree is an undirected connected graph with exactly n - 1 edges, which guarantees that there is exactly one simple path between any two nodes. Each edge has a positive weight. For every query [u, v] , we look at...

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LeetCode 3559 - Number of Ways to Assign Edge Weights II

LeetCode Problem 3559 Difficulty: 🔴 Hard Topics: Array, Math, Dynamic Programming, Bit Manipulation, Tree, Depth-First Search Solution Problem Understanding We are given an undirected tree with n nodes, rooted at node 1 . Every edge will eventually receive a weight of either 1 or 2 . For each query [u, v] , we only care about the unique path connecting u and v . All edges outside that path are...

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LeetCode 3553 - Minimum Weighted Subgraph With the Required Paths II

LeetCode Problem 3553 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Bit Manipulation, Tree, Depth-First Search Solution Problem Understanding We are given a weighted, undirected tree with n nodes. Because the graph is a tree, there is exactly one simple path between any two nodes. For each query [src1, src2, dest] , we must find the minimum total weight of a connected subtree such that both src1 and src2 can reach...

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LeetCode 3533 - Concatenated Divisibility

LeetCode Problem 3533 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Bit Manipulation, Bitmask Solution LeetCode 3533 - Concatenated Divisibility Problem Understanding We are given an array nums containing up to 13 positive integers and an integer k . We may reorder the numbers in any permutation. After choosing an ordering, we concatenate the decimal representations of the numbers to form a single large integer. The task is to find a...

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LeetCode 3530 - Maximum Profit from Valid Topological Order in DAG

LeetCode Problem 3530 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Bit Manipulation, Graph Theory, Topological Sort, Bitmask Solution Problem Understanding The problem requires computing the maximum possible profit achievable by processing nodes of a Directed Acyclic Graph (DAG) in a valid topological order . Each node has a score, and the profit contribution of a node is its score multiplied by its position in the processing order (1-based). The goal...

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LeetCode 3514 - Number of Unique XOR Triplets II

LeetCode Problem 3514 Difficulty: 🟡 Medium Topics: Array, Math, Bit Manipulation, Enumeration Solution LeetCode 3514 - Number of Unique XOR Triplets II Problem Understanding We are given an integer array nums , and we must consider every triplet of indices (i, j, k) such that i <= j <= k . For each valid triplet, we compute: $$nums[i] \oplus nums[j] \oplus nums[k]$$ where ⊕ denotes the bitwise XOR operation. The...

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LeetCode 3513 - Number of Unique XOR Triplets I

LeetCode Problem 3513 Difficulty: 🟡 Medium Topics: Array, Math, Bit Manipulation Solution Problem Understanding The problem asks us to determine the number of unique values that can result from taking the XOR of three elements in a given array nums , where the triplets (i, j, k) must satisfy i <= j <= k . Importantly, nums is a permutation of integers from 1 to n , meaning every integer...

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LeetCode 3444 - Minimum Increments for Target Multiples in an Array

LeetCode Problem 3444 Difficulty: 🔴 Hard Topics: Array, Math, Dynamic Programming, Bit Manipulation, Number Theory, Bitmask Solution LeetCode 3444 - Minimum Increments for Target Multiples in an Array Problem Understanding We are given two arrays: nums , the array whose elements we are allowed to increase. target , a small array containing values that must each be represented by at least one multiple somewhere in the final version of nums...

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LeetCode 3435 - Frequencies of Shortest Supersequences

LeetCode Problem 3435 Difficulty: 🔴 Hard Topics: Array, String, Bit Manipulation, Graph Theory, Topological Sort, Enumeration Solution Problem Understanding The problem asks us to find all shortest common supersequences (SCS) of a given list of two-character strings words . A shortest common supersequence is a string of minimum length that contains each word in words as a subsequence. Importantly, the output should not include SCSs that are permutations of each...

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LeetCode 3376 - Minimum Time to Break Locks I

LeetCode Problem 3376 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Backtracking, Bit Manipulation, Breadth-First Search, Bitmask Solution LeetCode 3376 - Minimum Time to Break Locks I Problem Understanding The problem describes a sequence of locks that must all be broken. Each lock requires a certain amount of energy, given by strength[i] . Bob's sword starts with: Energy = 0 Growth factor x = 1 Every minute, the sword gains x...

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LeetCode 3108 - Minimum Cost Walk in Weighted Graph

LeetCode Problem 3108 Difficulty: 🔴 Hard Topics: Array, Bit Manipulation, Union-Find, Graph Theory Solution Problem Understanding This problem gives us an undirected weighted graph with n vertices and up to 10^5 edges. Each edge connects two vertices and has an integer weight. For every query [s, t] , we must determine the minimum possible cost of any walk from node s to node t . The key detail is the...

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LeetCode 2527 - Find Xor-Beauty of Array

LeetCode Problem 2527 Difficulty: 🟡 Medium Topics: Array, Math, Bit Manipulation Solution Problem Understanding The problem defines a special value called the "effective value" for every possible triplet of indices (i, j, k) in the array: $$((nums[i] \mid nums[j]) & nums[k])$$ where: | is the bitwise OR operator & is the bitwise AND operator The xor-beauty of the array is the XOR of the effective values for all possible triplets....

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LeetCode 3191 - Minimum Operations to Make Binary Array Elements Equal to One I

LeetCode Problem 3191 Difficulty: 🟡 Medium Topics: Array, Bit Manipulation, Queue, Sliding Window, Prefix Sum Solution Problem Understanding We are given a binary array nums consisting only of 0s and 1s. We are allowed to perform an operation any number of times: choose any three consecutive elements and flip them, meaning 0 becomes 1 and 1 becomes 0. The goal is to determine the minimum number of such operations required...

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LeetCode 1787 - Make the XOR of All Segments Equal to Zero

LeetCode Problem 1787 Difficulty: 🔴 Hard Topics: Array, Hash Table, Dynamic Programming, Bit Manipulation, Counting Solution Problem Understanding The problem is asking us to modify an array nums such that the XOR of all contiguous subarrays (segments) of length k is equal to zero, while minimizing the number of changes. Each element of nums is a non-negative integer less than $2^{10} = 1024$. The input array has a length up...

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LeetCode 2749 - Minimum Operations to Make the Integer Zero

LeetCode Problem 2749 Difficulty: 🟡 Medium Topics: Bit Manipulation, Brainteaser, Enumeration Solution Problem Understanding The problem gives us two integers, num1 and num2 . In one operation, we may choose any integer i between 0 and 60 , inclusive, and subtract the value 2^i + num2 from num1 . The goal is to determine the minimum number of operations required to make num1 become exactly 0 . If it is...

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LeetCode 3315 - Construct the Minimum Bitwise Array II

LeetCode Problem 3315 Difficulty: 🟡 Medium Topics: Array, Bit Manipulation Solution LeetCode 3315 - Construct the Minimum Bitwise Array II Problem Understanding We are given an array nums where every element is a prime number. For each value nums[i] , we must find the smallest non-negative integer ans[i] such that: $$ans[i] ;|; (ans[i] + 1) = nums[i]$$ where | denotes the bitwise OR operation. If no such value exists, we...

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LeetCode 2680 - Maximum OR

LeetCode Problem 2680 Difficulty: 🟡 Medium Topics: Array, Greedy, Bit Manipulation, Prefix Sum Solution Problem Understanding In this problem, we are given an integer array nums and an integer k . We may perform at most k operations, where each operation selects one element and multiplies it by 2 . Multiplying by 2 in binary is equivalent to shifting all bits one position to the left. For example: 5 in...

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LeetCode 3133 - Minimum Array End

LeetCode Problem 3133 Difficulty: 🟡 Medium Topics: Bit Manipulation Solution Problem Understanding The problem asks us to construct a strictly increasing array nums of length n such that the bitwise AND of all elements equals x . Among all valid arrays, we want to minimize the last element, nums[n - 1] . The constraints are important: Every element must be a positive integer. The array must be strictly increasing. The...

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LeetCode 2546 - Apply Bitwise Operations to Make Strings Equal

LeetCode Problem 2546 Difficulty: 🟡 Medium Topics: String, Bit Manipulation Solution Problem Understanding The problem provides two binary strings, s and target , of equal length n . You are allowed to perform a specific bitwise operation on s any number of times, which involves picking two distinct indices i and j and updating s[i] to s[i] OR s[j] and s[j] to s[i] XOR s[j] . The goal is to...

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LeetCode 1947 - Maximum Compatibility Score Sum

LeetCode Problem 1947 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Backtracking, Bit Manipulation, Bitmask Solution Problem Understanding The problem is asking us to optimally pair students with mentors such that the sum of their compatibility scores is maximized. Each student and each mentor has answered n yes/no questions represented by 0 s and 1 s. A student-mentor pair's compatibility score is the count of matching answers. For instance, if a...

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LeetCode 2568 - Minimum Impossible OR

LeetCode Problem 2568 Difficulty: 🟡 Medium Topics: Array, Bit Manipulation, Brainteaser Solution Problem Understanding The problem asks us to find the smallest positive integer that cannot be represented as a bitwise OR of any subsequence of a given array nums . The input array contains positive integers, and the subsequences can have any length, including length 1. The output must be the smallest integer greater than zero that cannot be...

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LeetCode 2846 - Minimum Edge Weight Equilibrium Queries in a Tree

LeetCode Problem 2846 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Bit Manipulation, Tree, Depth-First Search Solution Problem Understanding You are given an undirected weighted tree with n nodes. Since the graph is a tree, there is exactly one simple path between any two nodes. Each edge has a weight between 1 and 26 . For every query [a, b] , we look at the unique path from node a to...

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LeetCode 3283 - Maximum Number of Moves to Kill All Pawns

LeetCode Problem 3283 Difficulty: 🔴 Hard Topics: Array, Math, Bit Manipulation, Breadth-First Search, Game Theory, Bitmask Solution Problem Understanding The problem gives us a 50 x 50 chessboard containing exactly one knight and up to 15 pawns. The knight starts at position (kx, ky) , and every pawn is placed at one of the coordinates in positions . Two players, Alice and Bob, alternate turns. Alice moves first. During a...

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LeetCode 1908 - Game of Nim

LeetCode Problem 1908 Difficulty: 🟡 Medium Topics: Array, Math, Dynamic Programming, Bit Manipulation, Brainteaser, Game Theory Solution Problem Understanding This problem is the classic mathematical game known as Nim. We are given an array piles , where each element represents the number of stones in a pile. Two players, Alice and Bob, take turns removing stones. On each turn, a player may choose any non-empty pile and remove any positive...

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LeetCode 1994 - The Number of Good Subsets

LeetCode Problem 1994 Difficulty: 🔴 Hard Topics: Array, Hash Table, Math, Dynamic Programming, Bit Manipulation, Counting, Number Theory, Bitmask Solution LeetCode 1994 - The Number of Good Subsets Problem Understanding This problem asks us to count how many subsets of the input array have a product that can be written as a multiplication of distinct prime numbers. The phrase "distinct prime numbers" is the key restriction. A product is valid...

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LeetCode 2206 - Divide Array Into Equal Pairs

LeetCode Problem 2206 Difficulty: 🟢 Easy Topics: Array, Hash Table, Bit Manipulation, Counting Solution Problem Understanding The problem gives us an integer array nums containing exactly 2 * n elements. Our task is to determine whether it is possible to split the array into n valid pairs, where each pair contains two identical numbers. In simpler terms, every number in the array must be matched with another occurrence of the...

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LeetCode 2917 - Find the K-or of an Array

LeetCode Problem 2917 Difficulty: 🟢 Easy Topics: Array, Bit Manipulation Solution LeetCode 2917 - Find the K-or of an Array Problem Understanding This problem introduces a generalized version of the bitwise OR operation called the K-or . In a normal bitwise OR, a bit in the result becomes 1 if at least one number has that bit set. The K-or operation changes this rule. Instead of requiring one occurrence, a...

Practice › LeetCode › LeetCode 21xx ›

LeetCode 2128 - Remove All Ones With Row and Column Flips

LeetCode Problem 2128 Difficulty: 🟡 Medium Topics: Array, Math, Bit Manipulation, Matrix Solution Problem Understanding The problem gives us an m x n binary matrix named grid , where every cell contains either 0 or 1 . We are allowed to perform two kinds of operations: Flip an entire row Flip an entire column Flipping means changing every 0 into 1 and every 1 into 0 . Our goal is...

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LeetCode 2857 - Count Pairs of Points With Distance k

LeetCode Problem 2857 Difficulty: 🟡 Medium Topics: Array, Hash Table, Bit Manipulation Solution LeetCode 2857 - Count Pairs of Points With Distance k Problem Understanding We are given a list of 2D points, where each point is represented as [x, y] , and an integer k . The distance between two points is not the usual Euclidean or Manhattan distance. Instead, it is defined as: $$(x_1 \oplus x_2) + (y_1...

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LeetCode 2571 - Minimum Operations to Reduce an Integer to 0

LeetCode Problem 2571 Difficulty: 🟡 Medium Topics: Dynamic Programming, Greedy, Bit Manipulation Solution Problem Understanding The problem asks us to find the minimum number of operations required to reduce a given positive integer n to 0 , where each operation consists of adding or subtracting a power of two from the current value of n . A power of two is defined as any number of the form $2^i$ where...

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LeetCode 2939 - Maximum Xor Product

LeetCode Problem 2939 Difficulty: 🟡 Medium Topics: Math, Greedy, Bit Manipulation Solution That will be quite long and detailed given your required structure and depth. To ensure quality and avoid truncation, I will provide it in a carefully structured, complete editorial format. Before I begin, one important clarification: for LeetCode 2939 - Maximum Xor Product , there are two valid optimal explanations commonly used: Greedy bit construction with balancing intuition...

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LeetCode 3215 - Count Triplets with Even XOR Set Bits II

LeetCode Problem 3215 Difficulty: 🟡 Medium Topics: Array, Bit Manipulation Solution Problem Understanding The problem asks us to count the number of triplets (a[i], b[j], c[k]) from three integer arrays a , b , and c such that the bitwise XOR of the three numbers has an even number of set bits (bits equal to 1 in binary representation). In other words, if we compute a[i] XOR b[j] XOR c[k]...

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LeetCode 2419 - Longest Subarray With Maximum Bitwise AND

LeetCode Problem 2419 Difficulty: 🟡 Medium Topics: Array, Bit Manipulation, Brainteaser Solution Problem Understanding The problem asks us to find the length of the longest subarray within a given array nums such that the bitwise AND of all elements in that subarray is maximized . In simpler terms, we first need to identify the largest possible bitwise AND we can get from any subarray, and then determine the contiguous subarray(s)...

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LeetCode 3097 - Shortest Subarray With OR at Least K II

LeetCode Problem 3097 Difficulty: 🟡 Medium Topics: Array, Bit Manipulation, Sliding Window Solution LeetCode 3097 - Shortest Subarray With OR at Least K II Problem Understanding This problem asks us to find the smallest non-empty contiguous subarray whose bitwise OR is at least k . The input consists of: An integer array nums An integer k For any subarray nums[left:right+1] , we compute the bitwise OR of all elements inside...

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LeetCode 3304 - Find the K-th Character in String Game I

LeetCode Problem 3304 Difficulty: 🟢 Easy Topics: Math, Bit Manipulation, Recursion, Simulation Solution Problem Understanding The problem defines an infinite string-building process that starts with the string "a" . At every operation, we take the current string and create a transformed version where every character is replaced by the next character in the alphabet. Then we append this transformed string to the original string. For example: "a" becomes "ab" "ab"...

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LeetCode 2157 - Groups of Strings

LeetCode Problem 2157 Difficulty: 🔴 Hard Topics: Array, Hash Table, String, Bit Manipulation, Union-Find Solution Problem Understanding The problem asks us to group a list of unique lowercase strings based on a special notion of connectivity. Each string can be represented as a set of letters , and two strings are connected if one can be transformed into the other with exactly one operation : adding a letter, removing a...

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LeetCode 2959 - Number of Possible Sets of Closing Branches

LeetCode Problem 2959 Difficulty: 🔴 Hard Topics: Bit Manipulation, Graph Theory, Heap (Priority Queue), Enumeration, Shortest Path Solution Problem Understanding This problem asks us to determine the number of possible sets of branches that can be closed such that the maximum distance between any pair of remaining open branches does not exceed a given maxDistance . The input consists of n branches connected by undirected roads with given weights, where...

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LeetCode 3068 - Find the Maximum Sum of Node Values

LeetCode Problem 3068 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Greedy, Bit Manipulation, Tree, Sorting Solution Problem Understanding You are given a tree with n nodes. Every node has a value stored in the array nums , and every edge connects two nodes in an undirected manner. You may repeatedly perform the following operation on any edge [u, v] : Replace nums[u] with nums[u] XOR k Replace nums[v] with nums[v]...

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LeetCode 2506 - Count Pairs Of Similar Strings

LeetCode Problem 2506 Difficulty: 🟢 Easy Topics: Array, Hash Table, String, Bit Manipulation, Counting Solution Problem Understanding The problem gives us an array of strings called words . We must count how many pairs of indices (i, j) satisfy two conditions: i < j words[i] and words[j] are similar Two strings are considered similar if they contain exactly the same set of distinct characters, regardless of order or frequency. For...

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LeetCode 2247 - Maximum Cost of Trip With K Highways

LeetCode Problem 2247 Difficulty: 🔴 Hard Topics: Dynamic Programming, Bit Manipulation, Graph Theory, Bitmask Solution Problem Understanding The problem gives us an undirected weighted graph with n cities and a list of highways. Each highway connects two cities and has an associated toll cost. We must find the maximum possible total toll for a trip that uses exactly k highways. There are two important restrictions: We may start from any...

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LeetCode 2220 - Minimum Bit Flips to Convert Number

LeetCode Problem 2220 Difficulty: 🟢 Easy Topics: Bit Manipulation Solution Problem Understanding The problem asks us to determine the minimum number of bit flips required to transform an integer start into another integer goal . A bit flip is defined as changing a single bit in the binary representation of a number from 0 to 1 or from 1 to 0 . The input consists of two non-negative integers start...

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LeetCode 3094 - Guess the Number Using Bitwise Questions II

LeetCode Problem 3094 Difficulty: 🟡 Medium Topics: Bit Manipulation, Interactive Solution Before I write the full guide, I want to confirm one detail: for LeetCode 3094 - Guess the Number Using Bitwise Questions II , there are no public input/output examples in the problem statement because it is an interactive problem . I can still provide the complete reference guide with all requested sections, including: Problem Understanding Brute Force and...

Practice › LeetCode › LeetCode 28xx ›

LeetCode 2836 - Maximize Value of Function in a Ball Passing Game

LeetCode Problem 2836 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Bit Manipulation Solution Problem Understanding This problem presents a ball-passing game among n players, represented by an array receiver of length n . Each element receiver[i] indicates which player receives the ball when player i passes it. The game starts by selecting a player i as the first to hold the ball. The ball is then passed k times according...

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LeetCode 3154 - Find Number of Ways to Reach the K-th Stair

LeetCode Problem 3154 Difficulty: 🔴 Hard Topics: Math, Dynamic Programming, Bit Manipulation, Memoization, Combinatorics Solution Let's dive into a comprehensive solution guide for LeetCode 3154 - Find Number of Ways to Reach the K-th Stair . Problem Understanding This problem involves Alice navigating a staircase starting at stair 1, aiming to reach stair k . The staircase is theoretically infinite, starting at stair 0, and Alice has two operations available:...

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LeetCode 3344 - Maximum Sized Array

LeetCode Problem 3344 Difficulty: 🟡 Medium Topics: Binary Search, Bit Manipulation Solution LeetCode 3344 - Maximum Sized Array Problem Understanding We are given a non-negative integer s and need to determine the largest possible dimension n of a three-dimensional array A . The array has dimensions n × n × n , and every element is defined as: $$A[i][j][k] = i \times (j ;|; k)$$ where | denotes the bitwise...

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LeetCode 2657 - Find the Prefix Common Array of Two Arrays

LeetCode Problem 2657 Difficulty: 🟡 Medium Topics: Array, Hash Table, Bit Manipulation Solution Problem Understanding The problem provides two arrays, A and B , each a permutation of integers from 1 to n . A permutation means each number from 1 to n appears exactly once in the array. We are asked to compute a new array C , called the prefix common array , where C[i] represents the number...

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LeetCode 2683 - Neighboring Bitwise XOR

LeetCode Problem 2683 Difficulty: 🟡 Medium Topics: Array, Bit Manipulation Solution Problem Understanding The problem presents us with a binary array called derived of length n . This array is constructed from another binary array original of the same length using the bitwise XOR operation on adjacent elements. Specifically, each element derived[i] is the XOR of original[i] and original[i+1] , with a wrap-around at the end where derived[n-1] = original[n-1]...

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LeetCode 2871 - Split Array Into Maximum Number of Subarrays

LeetCode Problem 2871 Difficulty: 🟡 Medium Topics: Array, Greedy, Bit Manipulation Solution Problem Understanding The problem is asking us to split a given array of non-negative integers into contiguous subarrays in a way that maximizes the number of subarrays , while minimizing the sum of their bitwise AND scores . The score of a subarray is defined as the bitwise AND of all elements in that subarray. Since AND-ing any...

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LeetCode 3209 - Number of Subarrays With AND Value of K

LeetCode Problem 3209 Difficulty: 🔴 Hard Topics: Array, Binary Search, Bit Manipulation, Segment Tree Solution Problem Understanding The problem asks us to count how many contiguous subarrays of nums have a bitwise AND equal to k . A subarray is any contiguous segment of the array. For every possible subarray, we compute the bitwise AND of all elements inside it. If the result equals k , that subarray contributes to...

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LeetCode 2708 - Maximum Strength of a Group

LeetCode Problem 2708 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Backtracking, Greedy, Bit Manipulation, Sorting, Enumeration Solution Problem Understanding The problem asks us to select a non-empty subset of integers from a given array nums such that the product of the numbers in the subset is maximized. Each number represents a student’s exam score, and the subset represents a group of students. The "strength" of a group is the product...

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LeetCode 3307 - Find the K-th Character in String Game II

LeetCode Problem 3307 Difficulty: 🔴 Hard Topics: Math, Bit Manipulation, Recursion Solution Problem Understanding The problem describes a string manipulation game between Alice and Bob. Initially, Alice starts with a string word = "a" . Bob provides a list of operations, represented by the integer array operations . Each operation transforms word in a specific way: If operations[i] == 0 , Alice duplicates the current string by appending a copy...

Practice › LeetCode › LeetCode 23xx ›

LeetCode 2306 - Naming a Company

LeetCode Problem 2306 Difficulty: 🔴 Hard Topics: Array, Hash Table, String, Bit Manipulation, Enumeration Solution Problem Understanding The problem gives us a list of unique strings called ideas . We must repeatedly choose two different strings, swap their first characters, and determine whether the newly formed strings are both absent from the original list. If both newly generated names do not already exist in ideas , then the ordered pair...

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LeetCode 2897 - Apply Operations on Array to Maximize Sum of Squares

LeetCode Problem 2897 Difficulty: 🔴 Hard Topics: Array, Hash Table, Greedy, Bit Manipulation Solution Problem Understanding The problem presents an integer array nums and a positive integer k . You can perform a bitwise operation on any two distinct elements of the array any number of times. Specifically, for indices i and j , you update nums[i] to (nums[i] AND nums[j]) and nums[j] to (nums[i] OR nums[j]) . After applying...

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LeetCode 2732 - Find a Good Subset of the Matrix

LeetCode Problem 2732 Difficulty: 🔴 Hard Topics: Array, Hash Table, Bit Manipulation, Matrix Solution Problem Understanding The problem asks us to find a subset of rows in a binary matrix where each column’s sum in that subset is at most half of the number of rows chosen, rounded down. In simpler terms, if you pick some rows, no column should have too many 1s compared to the number of rows...

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LeetCode 2438 - Range Product Queries of Powers

LeetCode Problem 2438 Difficulty: 🟡 Medium Topics: Array, Bit Manipulation, Prefix Sum Solution Problem Understanding The problem defines a special array called powers . This array is built from the binary representation of n . Every positive integer can be uniquely represented as a sum of powers of two. For example: 15 = 1 + 2 + 4 + 8 13 = 1 + 4 + 8 10 = 2...

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LeetCode 2505 - Bitwise OR of All Subsequence Sums

LeetCode Problem 2505 Difficulty: 🟡 Medium Topics: Array, Math, Bit Manipulation, Brainteaser, Prefix Sum Solution LeetCode 2505 - Bitwise OR of All Subsequence Sums Problem Understanding This problem asks us to compute the bitwise OR of every possible subsequence sum of a given array. A subsequence is formed by choosing any subset of elements while preserving their original order. Since every element can either be included or excluded, an array...

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LeetCode 3141 - Maximum Hamming Distances

LeetCode Problem 3141 Difficulty: 🔴 Hard Topics: Array, Bit Manipulation, Breadth-First Search Solution Problem Understanding The problem asks us to compute the maximum Hamming distance for each element in an array of integers. The Hamming distance between two integers is defined as the number of positions where their binary representations differ. We are given an array nums and an integer m , and each element of nums is guaranteed to...

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LeetCode 3003 - Maximize the Number of Partitions After Operations

LeetCode Problem 3003 Difficulty: 🔴 Hard Topics: String, Dynamic Programming, Bit Manipulation, Bitmask Solution Problem Understanding The problem asks us to take a string s and an integer k and compute the maximum number of partitions we can create from s under a specific set of operations. First, we are allowed to change at most one character in the string to any other lowercase English letter. After that, we repeatedly...

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LeetCode 2275 - Largest Combination With Bitwise AND Greater Than Zero

LeetCode Problem 2275 Difficulty: 🟡 Medium Topics: Array, Hash Table, Bit Manipulation, Counting Solution Problem Understanding The problem asks us to find the largest possible group of numbers from the candidates array such that the bitwise AND of every number in that group is greater than 0 . A bitwise AND operation only keeps bits that are set to 1 in every participating number. For example: 6 = 110 14...

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LeetCode 2980 - Check if Bitwise OR Has Trailing Zeros

LeetCode Problem 2980 Difficulty: 🟢 Easy Topics: Array, Bit Manipulation Solution Problem Understanding The problem asks us to determine whether we can select two or more elements from a given array of positive integers such that their bitwise OR produces a number whose binary representation ends with at least one zero . In other words, the least significant bit of the OR result should be 0 . The input is...

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LeetCode 2044 - Count Number of Maximum Bitwise-OR Subsets

LeetCode Problem 2044 Difficulty: 🟡 Medium Topics: Array, Backtracking, Bit Manipulation, Enumeration Solution Problem Understanding The problem asks us to examine every possible non-empty subset of the given array nums and compute the bitwise OR value of each subset. Among all these OR values, we need to determine the maximum possible value, then count how many different subsets produce that maximum. A subset is formed by selecting any combination of...

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LeetCode 2741 - Special Permutations

LeetCode Problem 2741 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Bit Manipulation, Bitmask Solution Problem Understanding The problem asks us to count the number of special permutations of a given array of distinct positive integers nums . A permutation is special if, for every adjacent pair of elements nums[i] and nums[i+1] , one element divides the other evenly, that is, either nums[i] % nums[i+1] == 0 or nums[i+1] % nums[i]...

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LeetCode 2351 - First Letter to Appear Twice

LeetCode Problem 2351 Difficulty: 🟢 Easy Topics: Hash Table, String, Bit Manipulation, Counting Solution Problem Understanding The problem gives us a string s containing only lowercase English letters. We need to return the first letter whose second occurrence appears earliest in the string. This detail is extremely important. The problem is not asking for the first character that repeats somewhere later. Instead, it asks which character reaches its second appearance...

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LeetCode 1986 - Minimum Number of Work Sessions to Finish the Tasks

LeetCode Problem 1986 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Backtracking, Bit Manipulation, Bitmask Solution Problem Understanding This problem asks us to schedule a collection of tasks into the minimum number of work sessions. Each task has a fixed duration, and every work session has a maximum allowed length, sessionTime . A task cannot be split across multiple sessions. Once a task starts inside a session, it must fully complete...

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LeetCode 2411 - Smallest Subarrays With Maximum Bitwise OR

LeetCode Problem 2411 Difficulty: 🟡 Medium Topics: Array, Binary Search, Bit Manipulation, Sliding Window Solution Problem Understanding The problem asks us to find, for each index in a given array nums , the length of the shortest contiguous subarray starting at that index whose bitwise OR is equal to the maximum possible bitwise OR obtainable from that index onward . In other words, we need to look at all subarrays...

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LeetCode 2172 - Maximum AND Sum of Array

LeetCode Problem 2172 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Bit Manipulation, Bitmask Solution LeetCode 2172 - Maximum AND Sum of Array Problem Understanding This problem asks us to distribute a set of integers into numbered slots in a way that maximizes a scoring function based on bitwise AND operations. We are given: An integer array nums A number of slots, numSlots Each slot is numbered from 1 to numSlots...

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LeetCode 2920 - Maximum Points After Collecting Coins From All Nodes

LeetCode Problem 2920 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Bit Manipulation, Tree, Depth-First Search, Memoization Solution LeetCode 2920 - Maximum Points After Collecting Coins From All Nodes Problem Understanding We are given a tree with n nodes rooted at node 0 . Each node contains a certain number of coins. We must collect coins from every node while respecting the tree hierarchy, meaning a node can only be processed...

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LeetCode 2992 - Number of Self-Divisible Permutations

LeetCode Problem 2992 Difficulty: 🟡 Medium Topics: Array, Math, Dynamic Programming, Backtracking, Bit Manipulation, Number Theory, Bitmask Solution Problem Understanding The problem asks us to count how many permutations of the numbers 1 through n satisfy a special condition called self-divisible. We start with the array: [1, 2, 3, ..., n] We must rearrange these numbers into every possible permutation, then determine whether the permutation is valid. A permutation a...

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LeetCode 3064 - Guess the Number Using Bitwise Questions I

LeetCode Problem 3064 Difficulty: 🟡 Medium Topics: Bit Manipulation, Interactive Solution Problem Understanding The problem presents an interactive scenario where there is a hidden number n in the range [1, 2^30 - 1] . We are provided with an API commonSetBits(num) which returns the count of bits that are set in both n and num when performing a bitwise AND. In other words, commonSetBits(num) computes the number of positions where...

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LeetCode 2152 - Minimum Number of Lines to Cover Points

LeetCode Problem 2152 Difficulty: 🟡 Medium Topics: Array, Hash Table, Math, Dynamic Programming, Backtracking, Bit Manipulation, Geometry, Bitmask Solution Problem Understanding This problem asks us to determine the minimum number of straight lines needed to cover a given set of points on an X-Y plane. Each point is defined by its (x, y) coordinates, and a straight line can pass through any number of points as long as they are...

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LeetCode 2869 - Minimum Operations to Collect Elements

LeetCode Problem 2869 Difficulty: 🟢 Easy Topics: Array, Hash Table, Bit Manipulation Solution LeetCode 2869 - Minimum Operations to Collect Elements Problem Understanding This problem gives us an array nums and an integer k . We repeatedly perform an operation where we remove the last element of the array and add it to our collection. The goal is to determine the minimum number of such operations required so that our...

Practice › LeetCode › LeetCode 18xx ›

LeetCode 1803 - Count Pairs With XOR in a Range

LeetCode Problem 1803 Difficulty: 🔴 Hard Topics: Array, Bit Manipulation, Trie Solution LeetCode 1803 - Count Pairs With XOR in a Range Problem Understanding The problem gives us an integer array nums and two integers, low and high . We need to count how many index pairs (i, j) satisfy two conditions: i < j low <= nums[i] XOR nums[j] <= high The XOR operation compares bits between two numbers....

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LeetCode 3149 - Find the Minimum Cost Array Permutation

LeetCode Problem 3149 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Bit Manipulation, Bitmask Solution Problem Understanding The problem presents an array nums of length n that is a permutation of integers from 0 to n - 1 . We are asked to find a permutation perm of the same range [0, 1, 2, ..., n-1] that minimizes a special cost function defined as: $$\text{score}(perm) = |perm[0] - nums[perm[1]]| + |perm[1]...

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LeetCode 2305 - Fair Distribution of Cookies

LeetCode Problem 2305 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Backtracking, Bit Manipulation, Bitmask Solution Problem Understanding The problem asks us to distribute a set of cookie bags among k children such that the unfairness of the distribution is minimized. Here, unfairness is defined as the maximum total number of cookies any single child receives . The input consists of an array cookies where cookies[i] represents the number of cookies...

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LeetCode 2403 - Minimum Time to Kill All Monsters

LeetCode Problem 2403 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Bit Manipulation, Bitmask Solution Problem Understanding The problem is asking us to compute the minimum number of days required to defeat all monsters in an array power , where power[i] represents the strength of the i-th monster. You start with zero mana and gain mana daily, with the initial daily gain of 1 . After defeating a monster, your mana...

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LeetCode 3276 - Select Cells in Grid With Maximum Score

LeetCode Problem 3276 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Bit Manipulation, Matrix, Bitmask Solution Problem Understanding The problem requires us to select cells from a 2D matrix grid such that no two selected cells are in the same row, and all selected values are unique. Our goal is to maximize the sum of these selected values. In other words, for each row, we can choose at most one value,...

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LeetCode 3211 - Generate Binary Strings Without Adjacent Zeros

LeetCode Problem 3211 Difficulty: 🟡 Medium Topics: String, Backtracking, Bit Manipulation Solution Problem Understanding The problem asks us to generate every binary string of length n such that no substring of length 2 contains two consecutive zeros. A binary string contains only the characters "0" and "1" . A substring of length 2 means every adjacent pair of characters in the string. The condition says that every such pair must...

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LeetCode 2932 - Maximum Strong Pair XOR I

LeetCode Problem 2932 Difficulty: 🟢 Easy Topics: Array, Hash Table, Bit Manipulation, Trie, Sliding Window Solution Problem Understanding The problem gives us an integer array nums , and we must choose two numbers x and y from the array such that they form a strong pair . A pair is considered strong if: $$|x - y| \leq \min(x, y)$$ Among all valid strong pairs, we must compute the maximum possible...

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LeetCode 3173 - Bitwise OR of Adjacent Elements

LeetCode Problem 3173 Difficulty: 🟢 Easy Topics: Array, Bit Manipulation Solution Problem Understanding The problem gives us an integer array nums of length n . We must create and return a new array called answer of length n - 1 . For every index i , the value at answer[i] should be the result of applying the bitwise OR operation between two adjacent elements in the original array: $answer[i] =...

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LeetCode 2588 - Count the Number of Beautiful Subarrays

LeetCode Problem 2588 Difficulty: 🟡 Medium Topics: Array, Hash Table, Bit Manipulation, Prefix Sum Solution Problem Understanding The problem gives us an array nums , and we are allowed to repeatedly perform a special operation on pairs of elements. In one operation, we choose two different indices i and j , and also choose a bit position k such that both nums[i] and nums[j] currently have the k th bit...

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LeetCode 3199 - Count Triplets with Even XOR Set Bits I

LeetCode Problem 3199 Difficulty: 🟢 Easy Topics: Array, Bit Manipulation Solution Problem Understanding The problem gives us three integer arrays, a , b , and c . We must count how many triplets (a[i], b[j], c[k]) produce a bitwise XOR result with an even number of set bits. A set bit is a bit equal to 1 in the binary representation of a number. For example: 5 in binary is...

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LeetCode 3287 - Find the Maximum Sequence Value of Array

LeetCode Problem 3287 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Bit Manipulation Solution LeetCode 3287 - Find the Maximum Sequence Value of Array Problem Understanding We are given an array nums and an integer k . We must choose a subsequence of exactly 2 * k elements while preserving the original order of the array. After selecting the subsequence, we split it into two equal halves: The first k selected...

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LeetCode 2397 - Maximum Rows Covered by Columns

LeetCode Problem 2397 Difficulty: 🟡 Medium Topics: Array, Backtracking, Bit Manipulation, Matrix, Enumeration Solution Problem Understanding This problem asks us to maximize the number of rows covered in a binary matrix after selecting exactly numSelect columns. Each row is covered if all 1 s in that row are located in the selected columns, or if the row contains only 0 s. The input is an m x n binary matrix,...

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LeetCode 2572 - Count the Number of Square-Free Subsets

LeetCode Problem 2572 Difficulty: 🟡 Medium Topics: Array, Math, Dynamic Programming, Bit Manipulation, Number Theory, Bitmask Solution Problem Understanding The problem asks us to count all non-empty subsets of a given array nums such that the product of the elements in each subset is square-free . A square-free integer is an integer not divisible by the square of any prime greater than 1. In other words, in its prime factorization,...

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LeetCode 2595 - Number of Even and Odd Bits

LeetCode Problem 2595 Difficulty: 🟢 Easy Topics: Bit Manipulation Solution Problem Understanding The problem asks us to analyze the binary representation of a positive integer n and count how many 1 bits appear at even indices and how many appear at odd indices. Bit positions are counted from right to left , starting at index 0 . This means the least significant bit, the rightmost bit, is at index 0...

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LeetCode 3393 - Count Paths With the Given XOR Value

LeetCode Problem 3393 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Bit Manipulation, Matrix Solution Problem Understanding The problem gives us an m x n grid where each cell contains a small integer value. We start at the top left corner (0, 0) and must reach the bottom right corner (m - 1, n - 1) by moving only right or down. Along every path, we compute the XOR of all...

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LeetCode 1879 - Minimum XOR Sum of Two Arrays

LeetCode Problem 1879 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Bit Manipulation, Bitmask Solution Problem Understanding The problem asks us to take two integer arrays of equal length, nums1 and nums2 , and rearrange the elements of nums2 to minimize the XOR sum . The XOR sum is computed as (nums1[0] XOR nums2[0]) + (nums1[1] XOR nums2[1]) + ... + (nums1[n - 1] XOR nums2[n - 1]) . The task...

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LeetCode 3226 - Number of Bit Changes to Make Two Integers Equal

LeetCode Problem 3226 Difficulty: 🟢 Easy Topics: Bit Manipulation Solution Problem Understanding The problem gives us two positive integers, n and k . We are allowed to perform one specific operation on n : choose any bit that is currently 1 in the binary representation of n and change it to 0 . We are not allowed to: Change a 0 bit into 1 Change bits in k Rearrange bits...

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LeetCode 2429 - Minimize XOR

LeetCode Problem 2429 Difficulty: 🟡 Medium Topics: Greedy, Bit Manipulation Solution Problem Understanding The problem is asking us to construct an integer x that satisfies two conditions. First, x must have the same number of set bits (1's in the binary representation) as a given integer num2 . Second, the XOR of x with another integer num1 must be minimized. In other words, we want x XOR num1 to be...

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LeetCode 3007 - Maximum Number That Sum of the Prices Is Less Than or Equal to K

LeetCode Problem 3007 Difficulty: 🟡 Medium Topics: Math, Binary Search, Dynamic Programming, Bit Manipulation Solution Problem Understanding The problem asks us to find the largest integer num such that the accumulated price of all numbers from 1 to num does not exceed a given threshold k . The price of a single number is determined by the number of set bits (1s) at specific positions in its binary representation, specifically...

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LeetCode 2425 - Bitwise XOR of All Pairings

LeetCode Problem 2425 Difficulty: 🟡 Medium Topics: Array, Bit Manipulation, Brainteaser Solution Problem Understanding The problem gives us two arrays, nums1 and nums2 , and asks us to compute the XOR of every possible pair formed between the two arrays. For every element in nums1 , we pair it with every element in nums2 exactly once. Each pair produces a value using the bitwise XOR operation: nums1[i] ^ nums2[j] If...

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LeetCode 3095 - Shortest Subarray With OR at Least K I

LeetCode Problem 3095 Difficulty: 🟢 Easy Topics: Array, Bit Manipulation, Sliding Window Solution Problem Understanding The problem asks us to find the shortest subarray within a given array nums such that the bitwise OR of all elements in that subarray is at least k . A subarray is any contiguous sequence of elements in nums . The input array consists of non-negative integers , and the integer k is in...

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LeetCode 2850 - Minimum Moves to Spread Stones Over Grid

LeetCode Problem 2850 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Backtracking, Bit Manipulation, Matrix, Bitmask Solution Problem Understanding This problem asks us to take a 3x3 grid of integers representing stones in each cell and redistribute them so that every cell contains exactly one stone. Each move consists of moving a stone from one cell to a directly adjacent cell (sharing a side, not a diagonal). The goal is to...

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LeetCode 1863 - Sum of All Subset XOR Totals

LeetCode Problem 1863 Difficulty: 🟢 Easy Topics: Array, Math, Backtracking, Bit Manipulation, Combinatorics, Enumeration Solution LeetCode 1863 - Sum of All Subset XOR Totals Problem Understanding This problem asks us to compute the sum of the XOR values of every possible subset of a given array. A subset is formed by choosing any combination of elements from the array, including the empty subset and the full array itself. Since an...

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LeetCode 2174 - Remove All Ones With Row and Column Flips II

LeetCode Problem 2174 Difficulty: 🟡 Medium Topics: Array, Bit Manipulation, Breadth-First Search, Matrix Solution Problem Understanding The problem gives us an m x n binary matrix where every cell contains either 0 or 1 . Our goal is to remove all 1 s using the minimum number of operations. An operation can only be performed on a cell (i, j) that currently contains a 1 . Once we choose such...

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LeetCode 3022 - Minimize OR of Remaining Elements Using Operations

LeetCode Problem 3022 Difficulty: 🔴 Hard Topics: Array, Greedy, Bit Manipulation Solution Problem Understanding The problem presents an array nums of non-negative integers and an integer k . You are allowed to perform at most k operations, where each operation merges two adjacent elements using the bitwise AND operator. The goal is to minimize the bitwise OR of all remaining elements after performing these operations. Formally, if nums = [a_0,...

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LeetCode 2564 - Substring XOR Queries

LeetCode Problem 2564 Difficulty: 🟡 Medium Topics: Array, Hash Table, String, Bit Manipulation Solution Problem Understanding The problem gives us a binary string s and a list of queries. Each query contains two integers, first and second . For every query, we need to find a substring of s whose decimal value satisfies: $$val \oplus first = second$$ where ⊕ represents the bitwise XOR operation. We can rearrange the equation...

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LeetCode 3011 - Find if Array Can Be Sorted

LeetCode Problem 3011 Difficulty: 🟡 Medium Topics: Array, Bit Manipulation, Sorting Solution Here’s the complete, detailed technical solution guide for LeetCode 3011 - Find if Array Can Be Sorted , following your requested formatting and style: Problem Understanding The problem provides a 0-indexed array of positive integers nums . The task is to determine if the array can be sorted in ascending order by performing a series of adjacent swaps...

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LeetCode 3171 - Find Subarray With Bitwise OR Closest to K

LeetCode Problem 3171 Difficulty: 🔴 Hard Topics: Array, Binary Search, Bit Manipulation, Segment Tree Solution Problem Understanding The problem asks us to find a subarray within a given array nums such that the absolute difference between the integer k and the bitwise OR of the subarray elements is minimized. A subarray is any contiguous sequence of elements in the array, so we are looking for a segment of nums where...

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LeetCode 3370 - Smallest Number With All Set Bits

LeetCode Problem 3370 Difficulty: 🟢 Easy Topics: Math, Bit Manipulation Solution Problem Understanding The problem asks us to find the smallest integer x such that: x >= n Every bit in the binary representation of x is set to 1 A number whose binary representation contains only set bits looks like this: 1 → binary "1" 3 → binary "11" 7 → binary "111" 15 → binary "1111" These numbers...

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LeetCode 2354 - Number of Excellent Pairs

LeetCode Problem 2354 Difficulty: 🔴 Hard Topics: Array, Hash Table, Binary Search, Bit Manipulation Solution Problem Understanding The problem provides a 0-indexed array of positive integers nums and a positive integer k . The task is to count all distinct pairs (num1, num2) such that both numbers exist in nums and the sum of the number of set bits in num1 OR num2 and num1 AND num2 is at least...

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LeetCode 3145 - Find Products of Elements of Big Array

LeetCode Problem 3145 Difficulty: 🔴 Hard Topics: Array, Binary Search, Bit Manipulation Solution Problem Understanding The problem asks us to work with a conceptual infinite array called big_nums , which is generated by taking every positive integer i , converting it to its powerful array (the sorted array of powers of two that sum to i ), and concatenating all these arrays sequentially. For instance, 1 → [1] , 2...

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LeetCode 2835 - Minimum Operations to Form Subsequence With Target Sum

LeetCode Problem 2835 Difficulty: 🔴 Hard Topics: Array, Greedy, Bit Manipulation Solution Problem Understanding The problem presents a 0-indexed array nums of non-negative powers of 2 and an integer target . Each element in nums is guaranteed to be a power of two, which is important because it allows us to reason about sums and splits in terms of binary representation. You are allowed to perform a specific operation any...

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LeetCode 2151 - Maximum Good People Based on Statements

LeetCode Problem 2151 Difficulty: 🔴 Hard Topics: Array, Backtracking, Bit Manipulation, Enumeration Solution Problem Understanding The problem asks us to determine the maximum number of good people in a group given a set of statements about each other. Each person can either be good (always tells the truth) or bad (may lie or tell the truth). The input is a square 2D array statements of size n x n ,...

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LeetCode 3309 - Maximum Possible Number by Binary Concatenation

LeetCode Problem 3309 Difficulty: 🟡 Medium Topics: Array, Bit Manipulation, Enumeration Solution Problem Understanding The problem is asking for the maximum integer value that can be created by concatenating the binary representations of all elements in a list of three integers. Each number should be converted to its binary representation without leading zeros. After conversion, the binary strings can be concatenated in any order. The resulting binary string should then...

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LeetCode 2997 - Minimum Number of Operations to Make Array XOR Equal to K

LeetCode Problem 2997 Difficulty: 🟡 Medium Topics: Array, Bit Manipulation Solution Problem Understanding This problem asks us to transform an array so that the bitwise XOR of all elements becomes exactly k , while minimizing the number of operations. An operation consists of selecting any element in the array and flipping exactly one bit in its binary representation. A bit flip changes a 0 to 1 or a 1 to...

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LeetCode 2802 - Find The K-th Lucky Number

LeetCode Problem 2802 Difficulty: 🟡 Medium Topics: Math, String, Bit Manipulation Solution Problem Understanding This problem asks us to find the k-th lucky number , where a lucky number is defined as an integer consisting only of the digits 4 and 7 . For example, the sequence of lucky numbers in increasing order starts as 4, 7, 44, 47, 74, 77, 444, and so on. The input is a single...

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LeetCode 2135 - Count Words Obtained After Adding a Letter

LeetCode Problem 2135 Difficulty: 🟡 Medium Topics: Array, Hash Table, String, Bit Manipulation, Sorting Solution Problem Understanding The problem requires us to determine how many strings in targetWords can be formed from strings in startWords through a specific transformation. The transformation involves two operations: appending a single letter not already present in the string, and then rearranging all letters arbitrarily. Essentially, we are checking whether, by adding one new character...

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LeetCode 2859 - Sum of Values at Indices With K Set Bits

LeetCode Problem 2859 Difficulty: 🟢 Easy Topics: Array, Bit Manipulation Solution Problem Understanding The problem asks us to compute the sum of elements in an array, but not based on the values themselves. Instead, we decide whether to include an element by examining the binary representation of its index . You are given a 0-indexed integer array nums and an integer k . For each index i in the array,...

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LeetCode 2322 - Minimum Score After Removals on a Tree

LeetCode Problem 2322 Difficulty: 🔴 Hard Topics: Array, Bit Manipulation, Tree, Depth-First Search Solution That is a long, multi-section technical guide with code, worked examples, test cases, and detailed explanations. I can provide the full reference document, but it will be quite large. I’ll structure it exactly according to your required format for LeetCode 2322 - Minimum Score After Removals on a Tree , including: Problem Understanding Approaches (brute force...

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LeetCode 2433 - Find The Original Array of Prefix Xor

LeetCode Problem 2433 Difficulty: 🟡 Medium Topics: Array, Bit Manipulation Solution Problem Understanding The problem is asking us to reverse-engineer an array arr from its prefix XOR array pref . Specifically, pref[i] represents the XOR of all elements in arr from index 0 to i . Our goal is to reconstruct arr given only pref . For instance, if pref = [5,2,0,3,1] , it means: pref[0] = arr[0] pref[1] =...

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LeetCode 3117 - Minimum Sum of Values by Dividing Array

LeetCode Problem 3117 Difficulty: 🔴 Hard Topics: Array, Binary Search, Dynamic Programming, Bit Manipulation, Segment Tree, Queue Solution Problem Understanding This problem asks us to partition an array nums into exactly m contiguous subarrays such that the bitwise AND of elements in the i-th subarray equals andValues[i] . Once partitioned, we sum the last elements of each subarray to compute a total value, and the goal is to minimize this...

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LeetCode 3314 - Construct the Minimum Bitwise Array I

LeetCode Problem 3314 Difficulty: 🟢 Easy Topics: Array, Bit Manipulation Solution Problem Understanding The problem asks us to construct an array ans from a given array nums of prime integers. For each element nums[i] , we need to find the smallest integer ans[i] such that the bitwise OR of ans[i] and ans[i] + 1 equals nums[i] . Formally, ans[i] | (ans[i] + 1) == nums[i] . If no such ans[i]...

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LeetCode 3181 - Maximum Total Reward Using Operations II

LeetCode Problem 3181 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Bit Manipulation Solution Problem Understanding The problem gives us an array rewardValues , where each element represents a reward we may choose exactly once. We begin with a total reward x = 0 , and we are allowed to repeatedly pick an unmarked element only if its value is strictly greater than the current total reward. Once we choose a...

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LeetCode 3116 - Kth Smallest Amount With Single Denomination Combination

LeetCode Problem 3116 Difficulty: 🔴 Hard Topics: Array, Math, Binary Search, Bit Manipulation, Combinatorics, Number Theory Solution Problem Understanding The problem asks us to determine the kth smallest amount that can be formed using coins of given denominations under a strict limitation: we can only use a single type of coin at a time . In other words, combinations of different denominations are not allowed . The input consists of...

Practice › LeetCode › LeetCode 27xx ›

LeetCode 2791 - Count Paths That Can Form a Palindrome in a Tree

LeetCode Problem 2791 Difficulty: 🔴 Hard Topics: Hash Table, Bit Manipulation, Tree, Depth-First Search Solution I can do that, but the guide will be very long for a single chat response because your required format includes detailed prose, brute force and optimal approaches, proof sketch, Python and Go implementations, worked traces for every example, complexity analysis, comprehensive tests, and edge cases for a Hard problem. To avoid truncation and keep...

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LeetCode 2212 - Maximum Points in an Archery Competition

LeetCode Problem 2212 Difficulty: 🟡 Medium Topics: Array, Backtracking, Bit Manipulation, Enumeration Solution Problem Understanding The problem is asking us to determine the optimal way for Bob to distribute his numArrows across 12 scoring sections (from 0 to 11) in an archery competition in order to maximize his total points against Alice. Alice's arrow distribution is given in aliceArrows . The scoring rules are such that for each section, the...

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LeetCode 2317 - Maximum XOR After Operations

LeetCode Problem 2317 Difficulty: 🟡 Medium Topics: Array, Math, Bit Manipulation Solution Problem Understanding The problem gives us an integer array nums , and we may perform a special operation any number of times. In one operation, we choose an index i and any non-negative integer x , then replace: nums[i] = nums[i] AND (nums[i] XOR x) Our goal is to maximize the bitwise XOR of all elements in the...

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LeetCode 2184 - Number of Ways to Build Sturdy Brick Wall

LeetCode Problem 2184 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Bit Manipulation, Bitmask Solution Problem Understanding The problem asks us to compute the number of ways to build a wall of given height and width using bricks of specified widths, such that the wall is sturdy . A wall is sturdy if no two adjacent rows have bricks that meet at the same position horizontally, except at the ends of...

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LeetCode 2935 - Maximum Strong Pair XOR II

LeetCode Problem 2935 Difficulty: 🔴 Hard Topics: Array, Hash Table, Bit Manipulation, Trie, Sliding Window Solution Problem Understanding The problem asks us to find the maximum XOR value of a strong pair in a given array of integers nums . A pair (x, y) is considered strong if it satisfies the condition |x - y| <= min(x, y) . This means the difference between the two numbers cannot exceed the...

Practice › LeetCode › LeetCode 19xx ›

LeetCode 1915 - Number of Wonderful Substrings

LeetCode Problem 1915 Difficulty: 🟡 Medium Topics: Hash Table, String, Bit Manipulation, Prefix Sum Solution LeetCode 1915, Number of Wonderful Substrings Problem Understanding The problem asks us to count how many non-empty substrings of a given string are considered "wonderful". A substring is wonderful if at most one character appears an odd number of times inside that substring. The string only contains characters from 'a' to 'j' , which means...

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LeetCode 2401 - Longest Nice Subarray

LeetCode Problem 2401 Difficulty: 🟡 Medium Topics: Array, Bit Manipulation, Sliding Window Solution Problem Understanding The problem gives an array of positive integers and asks for the length of the longest contiguous subarray that is considered "nice". A subarray is nice when every pair of distinct elements inside it has a bitwise AND equal to 0 . In other words, for any two different numbers in the subarray: a &...

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LeetCode 1938 - Maximum Genetic Difference Query

LeetCode Problem 1938 Difficulty: 🔴 Hard Topics: Array, Hash Table, Bit Manipulation, Depth-First Search, Trie Solution Problem Understanding The problem presents a rooted tree where each node is uniquely identified by an integer from 0 to n-1 . This integer also represents the genetic value of the node. The tree structure is given by the parents array, where parents[i] indicates the parent of node i , and -1 indicates the...

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LeetCode 1930 - Unique Length-3 Palindromic Subsequences

LeetCode Problem 1930 Difficulty: 🟡 Medium Topics: Hash Table, String, Bit Manipulation, Prefix Sum Solution Problem Understanding The problem asks us to count unique palindromic subsequences of length 3 in a given string s . A palindromic string reads the same forwards and backwards, and in this case, we only care about strings of exactly three characters. A subsequence is formed by deleting zero or more characters from the original...

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LeetCode 2002 - Maximum Product of the Length of Two Palindromic Subsequences

LeetCode Problem 2002 Difficulty: 🟡 Medium Topics: String, Dynamic Programming, Backtracking, Bit Manipulation, Bitmask Solution Problem Understanding The problem is asking us to find two disjoint palindromic subsequences from a given string s such that the product of their lengths is maximized. A subsequence is derived by deleting zero or more characters from the original string while keeping the relative order intact. A palindrome reads the same forward and backward,...

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LeetCode 461 - Hamming Distance

LeetCode Problem 461 Difficulty: 🟢 Easy Topics: Bit Manipulation Solution Problem Understanding The problem asks us to compute the Hamming distance between two integers. The Hamming distance is defined as the number of bit positions where the two numbers differ in their binary representation. For example, consider x = 1 and y = 4 . Their binary representations are: 1 = 0001 4 = 0100 If we compare the bits...

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LeetCode 782 - Transform to Chessboard

LeetCode Problem 782 Difficulty: 🔴 Hard Topics: Array, Math, Bit Manipulation, Matrix Solution LeetCode 782 - Transform to Chessboard Problem Understanding This problem gives us an n x n binary matrix called board , where every cell contains either 0 or 1 . In one operation, we are allowed to swap any two rows or swap any two columns. The goal is to determine the minimum number of swaps required...

Practice › LeetCode › LeetCode 06xx ›

LeetCode 645 - Set Mismatch

LeetCode Problem 645 Difficulty: 🟢 Easy Topics: Array, Hash Table, Bit Manipulation, Sorting Solution Problem Understanding The problem describes a corrupted set of integers. Originally, the set contained every number from 1 through n exactly once. Because of an error, one number was duplicated, which means one other number disappeared. The input array nums represents this corrupted version of the set. Since one number appears twice and another is missing,...

Practice › LeetCode › LeetCode 16xx ›

LeetCode 1601 - Maximum Number of Achievable Transfer Requests

LeetCode Problem 1601 Difficulty: 🔴 Hard Topics: Array, Backtracking, Bit Manipulation, Enumeration Solution Problem Understanding The problem asks us to maximize the number of employee transfer requests that can be fulfilled under the constraint that the total number of employees in each building remains constant. Each request is represented as a pair [from, to] , indicating an employee wants to move from building from to building to . The challenge...

Practice › LeetCode › LeetCode 10xx ›

LeetCode 1009 - Complement of Base 10 Integer

LeetCode Problem 1009 Difficulty: 🟢 Easy Topics: Bit Manipulation Solution Problem Understanding This problem asks us to compute the complement of a base-10 integer by flipping every bit in its binary representation. For instance, if the input n is 5, its binary form is 101 . Flipping each 0 to 1 and each 1 to 0 produces 010 , which equals 2 in decimal. The input is guaranteed to be...

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LeetCode 638 - Shopping Offers

LeetCode Problem 638 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Backtracking, Bit Manipulation, Memoization, Bitmask Solution Problem Understanding This problem asks us to find the minimum cost to buy a set of items given individual prices and optional special offers. We are given three main inputs: an array price that specifies the unit price for each item, an array needs that specifies the exact number of each item we want...

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LeetCode 672 - Bulb Switcher II

LeetCode Problem 672 Difficulty: 🟡 Medium Topics: Math, Bit Manipulation, Depth-First Search, Breadth-First Search Solution Problem Understanding The problem describes a room containing n light bulbs, where every bulb starts in the on state. There are four buttons available, and each button flips a specific subset of bulbs. Flipping means changing on to off or off to on . The four buttons behave as follows: Button 1 flips every bulb....

Practice › LeetCode › LeetCode 17xx ›

LeetCode 1763 - Longest Nice Substring

LeetCode Problem 1763 Difficulty: 🟢 Easy Topics: Hash Table, String, Divide and Conquer, Bit Manipulation, Sliding Window Solution Problem Understanding The problem asks us to find the longest "nice" substring within a given string s . A substring is considered nice if for every letter it contains, both its lowercase and uppercase forms appear. For example, "aAa" is nice because it contains 'a' and 'A' . Conversely, "abA" is not...

Practice › LeetCode › LeetCode 16xx ›

LeetCode 1659 - Maximize Grid Happiness

LeetCode Problem 1659 Difficulty: 🔴 Hard Topics: Dynamic Programming, Bit Manipulation, Memoization, Bitmask Solution Problem Understanding This problem asks us to place introverts and extroverts inside an m x n grid in a way that maximizes the total happiness score. Every grid cell can either remain empty, contain one introvert, or contain one extrovert. We are allowed to leave some people unused, so we do not necessarily have to place...

Practice › LeetCode › LeetCode 14xx ›

LeetCode 1404 - Number of Steps to Reduce a Number in Binary Representation to One

LeetCode Problem 1404 Difficulty: 🟡 Medium Topics: String, Bit Manipulation, Simulation Solution Problem Understanding The problem gives us a binary number represented as a string s . Our task is to determine how many operations are required to reduce this number to exactly 1 . The allowed operations depend on whether the current value is even or odd: If the number is even, divide it by 2 If the number...

Practice › LeetCode › LeetCode 18xx ›

LeetCode 1829 - Maximum XOR for Each Query

LeetCode Problem 1829 Difficulty: 🟡 Medium Topics: Array, Bit Manipulation, Prefix Sum Solution Problem Understanding The problem gives us a sorted array nums and an integer maximumBit . For every query, we must choose a number k such that: 0 <= k < 2^maximumBit The value of: nums[0] XOR nums[1] XOR ... XOR nums[last] XOR k is as large as possible. After answering the query, we remove the last element...

Practice › LeetCode › LeetCode 09xx ›

LeetCode 957 - Prison Cells After N Days

LeetCode Problem 957 Difficulty: 🟡 Medium Topics: Array, Hash Table, Math, Bit Manipulation Solution Problem Understanding The problem presents a simulation scenario with a row of exactly 8 prison cells, where each cell is either occupied (1) or vacant (0). Each day, the state of a cell changes based on the states of its immediate neighbors. Specifically, a cell becomes occupied if both of its neighbors are in the same...

Practice › LeetCode › LeetCode 11xx ›

LeetCode 1125 - Smallest Sufficient Team

LeetCode Problem 1125 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Bit Manipulation, Bitmask Solution Problem Understanding This problem asks us to build the smallest possible team that collectively covers every required skill. We are given two inputs: req_skills , a list of unique required skills people , where people[i] contains the skills possessed by person i A team is considered sufficient if every skill in req_skills appears in at least...

Practice › LeetCode › LeetCode 17xx ›

LeetCode 1723 - Find Minimum Time to Finish All Jobs

LeetCode Problem 1723 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Backtracking, Bit Manipulation, Bitmask Solution Problem Understanding This problem is asking us to assign a set of jobs, each with a specific time requirement, to k workers such that every job is assigned to exactly one worker, and we minimize the maximum total working time among all workers. The input jobs is an integer array where jobs[i] represents the time...

Practice › LeetCode › LeetCode 04xx ›

LeetCode 473 - Matchsticks to Square

LeetCode Problem 473 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Backtracking, Bit Manipulation, Bitmask Solution LeetCode 473 - Matchsticks to Square Problem Understanding The problem gives us an array called matchsticks , where each element represents the length of a matchstick. The goal is to determine whether all of the matchsticks can be arranged to form exactly one square. A square has four equal sides, so the total length of...

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LeetCode 1680 - Concatenation of Consecutive Binary Numbers

LeetCode Problem 1680 Difficulty: 🟡 Medium Topics: Math, Bit Manipulation, Simulation Solution Problem Understanding The problem asks us to build a very large binary number by concatenating the binary representations of every integer from 1 through n , in order, and then return its decimal value modulo 10^9 + 7 . For example, if n = 3 : 1 in binary is "1" 2 in binary is "10" 3 in...

Practice › LeetCode › LeetCode 15xx ›

LeetCode 1521 - Find a Value of a Mysterious Function Closest to Target

LeetCode Problem 1521 Difficulty: 🔴 Hard Topics: Array, Binary Search, Bit Manipulation, Segment Tree Solution Problem Understanding The problem defines a mysterious function func(arr, l, r) that computes the bitwise AND of all elements in the subarray from index l to index r , inclusive. Formally, the function is: $func(arr,l,r)=arr[l]\ &\ arr[l+1]\ &\ \cdots\ &\ arr[r]$ We are given an integer array arr and a target value target . Our...

Practice › LeetCode › LeetCode 11xx ›

LeetCode 1177 - Can Make Palindrome from Substring

LeetCode Problem 1177 Difficulty: 🟡 Medium Topics: Array, Hash Table, String, Bit Manipulation, Prefix Sum Solution Problem Understanding The problem asks us to determine whether certain substrings of a given string s can be rearranged and partially modified to form a palindrome. A palindrome is a string that reads the same forward and backward. For each query [lefti, righti, ki] , we are allowed to take the substring s[lefti...righti] ,...

Practice › LeetCode › LeetCode 03xx ›

LeetCode 397 - Integer Replacement

LeetCode Problem 397 Difficulty: 🟡 Medium Topics: Dynamic Programming, Greedy, Bit Manipulation, Memoization Solution LeetCode 397 - Integer Replacement Problem Understanding The problem gives us a positive integer n and asks for the minimum number of operations required to transform it into 1 . At every step, we are allowed to apply one of two rules: If the number is even, we must divide it by 2 If the number...

Practice › LeetCode › LeetCode 08xx ›

LeetCode 898 - Bitwise ORs of Subarrays

LeetCode Problem 898 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Bit Manipulation Solution Problem Understanding The problem asks us to compute every possible bitwise OR value that can be formed from all non-empty contiguous subarrays of the given array arr , then return how many distinct values exist. A subarray is any contiguous slice of the array. For example, if arr = [1,2,4] , the valid subarrays are: [1] [2]...

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LeetCode 1617 - Count Subtrees With Max Distance Between Cities

LeetCode Problem 1617 Difficulty: 🔴 Hard Topics: Dynamic Programming, Bit Manipulation, Tree, Enumeration, Bitmask Solution Problem Understanding The input describes an undirected tree with n cities. Since the graph is a tree, there are exactly n - 1 edges and there is a unique simple path between every pair of cities. The problem asks us to examine every possible connected subset of cities. A subset is considered a valid subtree...

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LeetCode 89 - Gray Code

LeetCode Problem 89 Difficulty: 🟡 Medium Topics: Math, Backtracking, Bit Manipulation Solution LeetCode 89 - Gray Code Problem Understanding The problem asks us to generate a valid Gray code sequence for a given number of bits, n . A Gray code sequence is a special ordering of numbers where every adjacent pair differs by exactly one bit in binary form. In addition, the sequence is cyclic, meaning the first and...

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LeetCode 1720 - Decode XORed Array

LeetCode Problem 1720 Difficulty: 🟢 Easy Topics: Array, Bit Manipulation Solution Problem Understanding The problem gives us an encoded array where each element represents the XOR of two consecutive elements from an unknown original array. Specifically: encoded[i] = arr[i] XOR arr[i + 1] We are also given the first element of the original array, first = arr[0] . Using these two pieces of information, we must reconstruct the entire original...

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LeetCode 320 - Generalized Abbreviation

LeetCode Problem 320 Difficulty: 🟡 Medium Topics: String, Backtracking, Bit Manipulation Solution LeetCode 320, Generalized Abbreviation Problem Understanding This problem asks us to generate every possible generalized abbreviation of a given word. A generalized abbreviation is created by replacing some characters in the string with their count, while preserving the order of the remaining characters. The important restriction is that abbreviated sections must be non-overlapping and non-adjacent. In practice, this...

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LeetCode 1681 - Minimum Incompatibility

LeetCode Problem 1681 Difficulty: 🔴 Hard Topics: Array, Hash Table, Dynamic Programming, Bit Manipulation, Bitmask Solution Problem Understanding The problem is asking us to partition an integer array nums into exactly k subsets of equal size, such that no subset contains duplicate elements. The incompatibility of a subset is defined as the difference between its maximum and minimum values. Our goal is to find the minimum possible sum of these...

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LeetCode 1506 - Find Root of N-Ary Tree

LeetCode Problem 1506 Difficulty: 🟡 Medium Topics: Hash Table, Bit Manipulation, Tree, Depth-First Search Solution Problem Understanding This problem gives us every node of an N-ary tree in an arbitrary order, and asks us to determine which node is the root of the tree. An N-ary tree is a tree where each node can have zero or more children. Each node contains a unique integer value and a list of...

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LeetCode 371 - Sum of Two Integers

LeetCode Problem 371 Difficulty: 🟡 Medium Topics: Math, Bit Manipulation Solution Problem Understanding The problem asks us to compute the sum of two integers without using the arithmetic operators + and - . Instead of relying on normal arithmetic, we must use bit manipulation to simulate how addition works at the binary level. The input consists of two integers, a and b . These integers can be positive, negative, or...

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LeetCode 465 - Optimal Account Balancing

LeetCode Problem 465 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Backtracking, Bit Manipulation, Bitmask Solution Problem Understanding The problem gives a list of money transfers between people. Each transaction is represented as [from, to, amount] , meaning one person paid a certain amount to another person. After all transactions are completed, some people may owe money overall, while others are owed money overall. The goal is not to recreate the...

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LeetCode 756 - Pyramid Transition Matrix

LeetCode Problem 756 Difficulty: 🟡 Medium Topics: Hash Table, String, Backtracking, Bit Manipulation Solution Here’s a full, detailed technical solution guide for LeetCode 756 - Pyramid Transition Matrix , following your formatting rules precisely. Problem Understanding The problem is asking us to determine whether a pyramid of blocks can be constructed from a given bottom row of blocks, such that all blocks above obey certain triangular stacking rules. Each block...

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LeetCode 1525 - Number of Good Ways to Split a String

LeetCode Problem 1525 Difficulty: 🟡 Medium Topics: Hash Table, String, Dynamic Programming, Bit Manipulation Solution Problem Understanding The problem asks us to count how many ways we can split a string into two non-empty parts such that both parts contain the same number of distinct characters. A split occurs between two adjacent characters. For a string of length n , there are exactly n - 1 possible split positions because...

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LeetCode 1486 - XOR Operation in an Array

LeetCode Problem 1486 Difficulty: 🟢 Easy Topics: Math, Bit Manipulation Solution Problem Understanding The problem gives us two integers, n and start . We must construct an array named nums of length n , where each element is defined by the formula: $$nums[i] = start + 2 \times i$$ This means the array begins at start and increases by 2 for every next position. After constructing the array, we must...

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LeetCode 1066 - Campus Bikes II

LeetCode Problem 1066 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Backtracking, Bit Manipulation, Bitmask Solution That is a long-form technical guide with multiple required sections and detailed worked examples. I can provide the complete reference document, but it will be quite lengthy. I will include all requested sections: Problem Understanding Brute Force and Optimal Approaches Comparison Table Step-by-step Algorithm Walkthrough with proof sketch Complete Python Solution Complete Go Solution Fully...

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LeetCode 67 - Add Binary

LeetCode Problem 67 Difficulty: 🟢 Easy Topics: Math, String, Bit Manipulation, Simulation Solution LeetCode 67, Add Binary Problem Statement You are given two strings, a and b , where each string represents a binary number. A binary number contains only the characters '0' and '1' . The task is to add these two binary numbers together and return the result as another binary string. Unlike normal decimal addition, binary addition...

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LeetCode 1256 - Encode Number

LeetCode Problem 1256 Difficulty: 🟡 Medium Topics: Math, String, Bit Manipulation Solution Sure, let's build a full, detailed technical solution guide for LeetCode 1256 following your requested structure. Problem Understanding The problem asks us to take a non-negative integer num and encode it as a string using a secret encoding rule. The examples indicate that this encoding is not standard binary, decimal, or hexadecimal conversion, but follows a pattern where...

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LeetCode 401 - Binary Watch

LeetCode Problem 401 Difficulty: 🟢 Easy Topics: Backtracking, Bit Manipulation Solution Problem Understanding The problem describes a binary watch that uses LEDs to represent time. The watch has two sections. The top section contains 4 LEDs for the hour, and the bottom section contains 6 LEDs for the minutes. Each LED represents a binary digit. If an LED is on, it contributes its corresponding binary value. The hour LEDs can...

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LeetCode 864 - Shortest Path to Get All Keys

LeetCode Problem 864 Difficulty: 🔴 Hard Topics: Array, Bit Manipulation, Breadth-First Search, Matrix Solution Problem Understanding This problem asks us to find the shortest path to collect all keys in a 2D grid maze. The grid contains walls, open spaces, keys, locks, and a starting point. You can move in the four cardinal directions but cannot move diagonally, through walls, or outside the grid. Each lock can only be passed...

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LeetCode 1239 - Maximum Length of a Concatenated String with Unique Characters

LeetCode Problem 1239 Difficulty: 🟡 Medium Topics: Array, String, Backtracking, Bit Manipulation Solution Problem Understanding This problem asks us to select a subsequence of strings from the input array arr and concatenate them together such that the resulting string contains only unique characters. Among all valid concatenations, we must return the maximum possible length. A subsequence means we can either include or skip each string while preserving the original order....

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LeetCode 266 - Palindrome Permutation

LeetCode Problem 266 Difficulty: 🟢 Easy Topics: Hash Table, String, Bit Manipulation Solution Problem Understanding The problem asks whether the characters of a given string can be rearranged to form a palindrome. A palindrome is a string that reads the same forward and backward. Examples include "racecar" , "abba" , and "a" . The important detail is that we are not asked to actually generate the palindrome. We only need...

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LeetCode 338 - Counting Bits

LeetCode Problem 338 Difficulty: 🟢 Easy Topics: Dynamic Programming, Bit Manipulation Solution Problem Understanding The problem asks us to compute the number of set bits, also called population count or popcount, for every integer from 0 through n . A set bit is a bit with value 1 in the binary representation of a number. For example: 5 in binary is 101 , which contains two 1 bits 7 in...

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LeetCode 868 - Binary Gap

LeetCode Problem 868 Difficulty: 🟢 Easy Topics: Bit Manipulation Solution Problem Understanding The problem asks us to examine the binary representation of a positive integer n and determine the largest distance between two adjacent 1 bits. A binary number is made up of 0 s and 1 s. For example: 22 in binary is 10110 5 in binary is 101 8 in binary is 1000 We are interested only in...

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LeetCode 411 - Minimum Unique Word Abbreviation

LeetCode Problem 411 Difficulty: 🔴 Hard Topics: Array, String, Backtracking, Bit Manipulation Solution LeetCode 411 - Minimum Unique Word Abbreviation Problem Understanding This problem asks us to generate the shortest possible abbreviation for a given target word such that the abbreviation cannot also represent any word in the dictionary. An abbreviation replaces one or more non-adjacent substrings with their lengths. For example, the word "apple" can become: "5" because the...

Practice › LeetCode › LeetCode 07xx ›

LeetCode 751 - IP to CIDR

LeetCode Problem 751 Difficulty: 🟡 Medium Topics: String, Bit Manipulation Solution Problem Understanding This problem is asking us to take a starting IPv4 address and a number n of consecutive IP addresses and convert them into the minimal set of CIDR blocks that exactly covers that range. An IPv4 address is a 32-bit number written in the familiar dotted decimal format (e.g., "192.168.1.1" ), where each segment represents 8 bits....

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LeetCode 784 - Letter Case Permutation

LeetCode Problem 784 Difficulty: 🟡 Medium Topics: String, Backtracking, Bit Manipulation Solution Problem Understanding The problem asks us to generate every possible string that can be formed by independently changing the case of each alphabetic character in the input string. Digits cannot be modified, so they always remain the same in every generated result. Only English letters can change between lowercase and uppercase. For example, if the input is "a1b2"...

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LeetCode 1799 - Maximize Score After N Operations

LeetCode Problem 1799 Difficulty: 🔴 Hard Topics: Array, Math, Dynamic Programming, Backtracking, Bit Manipulation, Number Theory, Bitmask Solution Problem Understanding The problem asks us to maximize the total score obtained by performing n operations on an array nums of size 2 * n . In each operation, you select two elements from the array, calculate the greatest common divisor (GCD) of the two elements, multiply it by the operation index...

Practice › LeetCode › LeetCode 03xx ›

LeetCode 393 - UTF-8 Validation

LeetCode Problem 393 Difficulty: 🟡 Medium Topics: Array, Bit Manipulation Solution Problem Understanding The problem asks us to determine whether a sequence of integers represents a valid UTF-8 encoded byte stream. Each integer in the input array represents one byte, meaning only its lowest 8 bits matter. UTF-8 is a variable-length encoding system where a character may occupy between 1 and 4 bytes. The structure of the leading bits determines...

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LeetCode 861 - Score After Flipping Matrix

LeetCode Problem 861 Difficulty: 🟡 Medium Topics: Array, Greedy, Bit Manipulation, Matrix Solution Problem Understanding The problem provides an m x n binary matrix, grid , where each element is either 0 or 1 . You are allowed to perform a move , which consists of selecting any row or column and flipping all its values - turning every 0 into a 1 and every 1 into a 0 ....

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LeetCode 1755 - Closest Subsequence Sum

LeetCode Problem 1755 Difficulty: 🔴 Hard Topics: Array, Two Pointers, Dynamic Programming, Bit Manipulation, Sorting, Bitmask Solution Problem Understanding The problem asks us to find a subsequence of a given integer array nums such that the sum of that subsequence is as close as possible to a given integer goal . A subsequence can include any subset of elements in their original order, including the possibility of selecting none (which...

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LeetCode 231 - Power of Two

LeetCode Problem 231 Difficulty: 🟢 Easy Topics: Math, Bit Manipulation, Recursion Solution Problem Understanding The problem asks us to determine whether a given integer n is a power of two. A number is considered a power of two if it can be written in the form: $$n = 2^x$$ where x is a non-negative integer. Some examples of powers of two are: 1 = 2^0 2 = 2^1 4 =...

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LeetCode 1684 - Count the Number of Consistent Strings

LeetCode Problem 1684 Difficulty: 🟢 Easy Topics: Array, Hash Table, String, Bit Manipulation, Counting Solution Problem Understanding This problem asks us to determine how many strings in the words array are consistent with a given set of allowed characters. You are given two inputs: allowed , a string containing distinct lowercase English letters. words , an array of lowercase strings. A word is considered consistent if every character in that...

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LeetCode 1707 - Maximum XOR With an Element From Array

LeetCode Problem 1707 Difficulty: 🔴 Hard Topics: Array, Bit Manipulation, Trie Solution Problem Understanding The problem gives us two inputs: An integer array nums A list of queries, where each query is [xi, mi] For every query, we must find the maximum possible value of: nums[j] XOR xi subject to the condition: nums[j] <= mi If no number in nums satisfies the condition nums[j] <= mi , then the answer...

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LeetCode 1738 - Find Kth Largest XOR Coordinate Value

LeetCode Problem 1738 Difficulty: 🟡 Medium Topics: Array, Divide and Conquer, Bit Manipulation, Sorting, Heap (Priority Queue), Matrix, Prefix Sum, Quickselect Solution Problem Understanding The problem asks us to compute the XOR coordinate value for each element in a given 2D matrix and then find the kth largest among them. Specifically, for a coordinate (a, b) , the value is defined as the XOR of all elements in the submatrix...

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LeetCode 476 - Number Complement

LeetCode Problem 476 Difficulty: 🟢 Easy Topics: Bit Manipulation Solution Problem Understanding The problem asks us to compute the complement of a positive integer by flipping every bit in its binary representation. A binary complement means changing every 1 bit into 0 , and every 0 bit into 1 . For example, the integer 5 is represented in binary as 101 . Flipping each bit gives 010 , which is...

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LeetCode 1734 - Decode XORed Permutation

LeetCode Problem 1734 Difficulty: 🟡 Medium Topics: Array, Bit Manipulation Solution Problem Understanding The problem gives us an array called encoded , which was generated from an unknown permutation array perm . A permutation of the first n positive integers means the array contains every integer from 1 to n exactly once. For example: [1,2,3] is a valid permutation of 1..3 [2,4,1,5,3] is a valid permutation of 1..5 The encoding...

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LeetCode 805 - Split Array With Same Average

LeetCode Problem 805 Difficulty: 🔴 Hard Topics: Array, Hash Table, Math, Dynamic Programming, Bit Manipulation, Bitmask Solution Problem Understanding The problem asks whether we can divide the given array nums into two non-empty groups such that both groups have the same average. Suppose the array is split into subsets A and B . Let: sum(A) be the sum of elements in A len(A) be the number of elements in A...

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LeetCode 1542 - Find Longest Awesome Substring

LeetCode Problem 1542 Difficulty: 🔴 Hard Topics: Hash Table, String, Bit Manipulation Solution Problem Understanding The problem asks us to find the length of the longest awesome substring in a given string s consisting of digits. A substring is considered awesome if it can be rearranged (via any number of swaps) to form a palindrome. In other words, the characters in the substring can be permuted so that it reads...

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LeetCode 995 - Minimum Number of K Consecutive Bit Flips

LeetCode Problem 995 Difficulty: 🔴 Hard Topics: Array, Bit Manipulation, Queue, Sliding Window, Prefix Sum Solution Problem Understanding The problem gives us a binary array nums consisting of 0s and 1s and an integer k . The task is to transform the array so that all elements are 1 s using the minimum number of operations called k-bit flips . Each k-bit flip consists of picking a contiguous subarray of...

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LeetCode 1815 - Maximum Number of Groups Getting Fresh Donuts

LeetCode Problem 1815 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Bit Manipulation, Memoization, Bitmask Solution Problem Understanding This problem asks us to maximize the number of “happy” customer groups by choosing the best possible ordering of the groups. The donut shop produces donuts in batches of exactly batchSize . A fresh batch starts only when the previous batch has been completely consumed. A group is considered happy if the very...

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LeetCode 187 - Repeated DNA Sequences

LeetCode Problem 187 Difficulty: 🟡 Medium Topics: Hash Table, String, Bit Manipulation, Sliding Window, Rolling Hash, Hash Function Solution Problem Understanding This problem asks us to find all repeated DNA subsequences of a fixed length, specifically length 10 , inside a given DNA string. The input is a string s , where each character represents a DNA nucleotide. The string contains only four possible characters: 'A' 'C' 'G' 'T' We...

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LeetCode 1655 - Distribute Repeating Integers

LeetCode Problem 1655 Difficulty: 🔴 Hard Topics: Array, Hash Table, Dynamic Programming, Backtracking, Bit Manipulation, Counting, Bitmask Solution Problem Understanding This problem asks whether we can satisfy a set of customer requests using repeated integers from the array nums . Each customer wants a certain quantity of numbers, given by quantity[i] . The important restriction is that every number given to a single customer must be identical. A customer asking...

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LeetCode 1835 - Find XOR Sum of All Pairs Bitwise AND

LeetCode Problem 1835 Difficulty: 🔴 Hard Topics: Array, Math, Bit Manipulation Solution LeetCode 1835 - Find XOR Sum of All Pairs Bitwise AND Problem Understanding This problem asks us to compute the XOR sum of every possible pairwise bitwise AND between two arrays. More formally, for every pair (i, j) : Take arr1[i] AND arr2[j] Add that result to a conceptual list Compute the XOR of all values in that...

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LeetCode 832 - Flipping an Image

LeetCode Problem 832 Difficulty: 🟢 Easy Topics: Array, Two Pointers, Bit Manipulation, Matrix, Simulation Solution Problem Understanding The problem requires transforming an n x n binary matrix in two steps: first flipping it horizontally, then inverting it. Horizontally flipping a row means reversing the order of elements in that row, so the first element becomes last, the second becomes second-to-last, and so on. Inverting a row means changing all 0...

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LeetCode 691 - Stickers to Spell Word

LeetCode Problem 691 Difficulty: 🔴 Hard Topics: Array, Hash Table, String, Dynamic Programming, Backtracking, Bit Manipulation, Memoization, Bitmask Solution Let's dive deep into a detailed technical solution guide for LeetCode 691, following your formatting rules exactly. Problem Understanding The problem asks us to construct a target string using letters cut from an unlimited supply of given stickers, where each sticker is a lowercase word. You can reuse stickers multiple times...

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LeetCode 1558 - Minimum Numbers of Function Calls to Make Target Array

LeetCode Problem 1558 Difficulty: 🟡 Medium Topics: Array, Greedy, Bit Manipulation Solution Problem Understanding This problem asks us to transform an initial array arr of zeros into a target array nums using a minimal number of operations. There are two allowed operations: incrementing any single element of the array by 1, or doubling all elements of the array. The goal is to count the minimum total operations required to reach...

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LeetCode 222 - Count Complete Tree Nodes

LeetCode Problem 222 Difficulty: 🟢 Easy Topics: Binary Search, Bit Manipulation, Tree, Binary Tree Solution Problem Understanding The problem asks us to count how many nodes exist in a complete binary tree. A complete binary tree has a very specific structure. Every level except possibly the last one is completely filled, and the nodes on the final level appear as far left as possible. The input is the root node...

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LeetCode 1494 - Parallel Courses II

LeetCode Problem 1494 Difficulty: 🔴 Hard Topics: Dynamic Programming, Bit Manipulation, Graph Theory, Bitmask Solution Problem Understanding The problem asks us to determine the minimum number of semesters required to complete n courses when there are prerequisite constraints between some courses and a limit k on the number of courses that can be taken in a single semester. The input consists of an integer n , a list of prerequisite...

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LeetCode 847 - Shortest Path Visiting All Nodes

LeetCode Problem 847 Difficulty: 🔴 Hard Topics: Dynamic Programming, Bit Manipulation, Breadth-First Search, Graph Theory, Bitmask Solution Problem Understanding The problem gives us an undirected and connected graph with n nodes labeled from 0 to n - 1 . The graph is represented as an adjacency list, where graph[i] contains all nodes directly connected to node i . We must compute the length of the shortest path that visits every...

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LeetCode 698 - Partition to K Equal Sum Subsets

LeetCode Problem 698 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Backtracking, Bit Manipulation, Memoization, Bitmask Solution Problem Understanding The problem is asking whether an array of integers nums can be divided into exactly k subsets such that each subset has the same sum. The input consists of the integer array nums and the integer k . The expected output is a boolean value: true if such a partitioning is possible,...

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LeetCode 1386 - Cinema Seat Allocation

LeetCode Problem 1386 Difficulty: 🟡 Medium Topics: Array, Hash Table, Greedy, Bit Manipulation Solution Here is a complete, detailed technical solution guide for LeetCode 1386 - Cinema Seat Allocation in a single, comprehensive response following your formatting rules. Problem Understanding The problem describes a cinema with n rows, each containing exactly ten seats, labelled 1 through 10. Some of these seats are already reserved, given in the input array reservedSeats...

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LeetCode 526 - Beautiful Arrangement

LeetCode Problem 526 Difficulty: 🟡 Medium Topics: Array, Dynamic Programming, Backtracking, Bit Manipulation, Bitmask Solution Problem Understanding The problem asks us to count how many permutations of the integers from 1 to n satisfy a special divisibility condition. A permutation is an arrangement of all numbers from 1 to n where every number appears exactly once. For example, when n = 3 , the possible permutations include [1,2,3] , [2,1,3]...

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LeetCode 1318 - Minimum Flips to Make a OR b Equal to c

LeetCode Problem 1318 Difficulty: 🟡 Medium Topics: Bit Manipulation Solution Problem Understanding The problem gives us three positive integers, a , b , and c . We are allowed to flip individual bits in either a or b . A flip means changing a bit from 0 to 1 or from 1 to 0 . Our goal is to perform the minimum number of bit flips so that: (a OR...

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LeetCode 2032 - Two Out of Three

LeetCode Problem 2032 Difficulty: 🟢 Easy Topics: Array, Hash Table, Bit Manipulation Solution Problem Understanding The problem asks us to identify all distinct integers that appear in at least two out of three given integer arrays . The input consists of three arrays nums1 , nums2 , and nums3 , each containing integers in the range [1, 100] . The output is an array of integers that occur in at...

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LeetCode 1442 - Count Triplets That Can Form Two Arrays of Equal XOR

LeetCode Problem 1442 Difficulty: 🟡 Medium Topics: Array, Hash Table, Math, Bit Manipulation, Prefix Sum Solution Problem Understanding The problem asks us to find the number of triplets (i, j, k) in an array arr such that the XOR of elements from index i to j-1 equals the XOR of elements from index j to k . Formally, for 0 <= i < j <= k < arr.length , define:...

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LeetCode 1371 - Find the Longest Substring Containing Vowels in Even Counts

LeetCode Problem 1371 Difficulty: 🟡 Medium Topics: Hash Table, String, Bit Manipulation, Prefix Sum Solution LeetCode 1371 - Find the Longest Substring Containing Vowels in Even Counts Problem Understanding This problem asks us to find the length of the longest contiguous substring in which every vowel appears an even number of times. The vowels we care about are: a e i o u A vowel may appear zero times, and...

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LeetCode 1284 - Minimum Number of Flips to Convert Binary Matrix to Zero Matrix

LeetCode Problem 1284 Difficulty: 🔴 Hard Topics: Array, Hash Table, Bit Manipulation, Breadth-First Search, Matrix Solution Problem Understanding The problem asks us to transform a given binary matrix mat into a zero matrix, where all elements are 0 . Each operation allows you to flip a cell and its four immediate neighbors (up, down, left, right). Flipping means changing a 1 to 0 or a 0 to 1 . The...

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LeetCode 1018 - Binary Prefix Divisible By 5

LeetCode Problem 1018 Difficulty: 🟢 Easy Topics: Array, Bit Manipulation Solution Problem Understanding The problem presents a binary array nums , where each element is either 0 or 1 . We are asked to compute the sequence of numbers formed by interpreting the subarray nums[0..i] as a binary number, denoted as xi . The task is to return a boolean array indicating, for each i , whether xi is divisible...

Practice › LeetCode › LeetCode 03xx ›

LeetCode 342 - Power of Four

LeetCode Problem 342 Difficulty: 🟢 Easy Topics: Math, Bit Manipulation, Recursion Solution LeetCode 342 - Power of Four Problem Understanding This problem asks us to determine whether a given integer n is an exact power of four. In other words, we need to check whether there exists some integer x such that: n = 4^x Examples of powers of four are: 1 = 4^0 4 = 4^1 16 = 4^2...

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LeetCode 491 - Non-decreasing Subsequences

LeetCode Problem 491 Difficulty: 🟡 Medium Topics: Array, Hash Table, Backtracking, Bit Manipulation Solution LeetCode 491 - Non-decreasing Subsequences Problem Understanding The problem gives us an integer array nums and asks us to return every distinct subsequence that is non-decreasing and has length at least two. A subsequence is formed by deleting zero or more elements from the array without changing the relative order of the remaining elements. Unlike subarrays,...

Practice › LeetCode › LeetCode 03xx ›

LeetCode 351 - Android Unlock Patterns

LeetCode Problem 351 Difficulty: 🟡 Medium Topics: Dynamic Programming, Backtracking, Bit Manipulation, Bitmask Solution Problem Understanding The problem models the Android lock screen as a 3 x 3 grid containing digits 1 through 9 . A valid unlock pattern is a sequence of distinct dots that follows a special movement rule. The first rule is straightforward: each dot can only be used once in a pattern. This means every pattern...

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LeetCode 421 - Maximum XOR of Two Numbers in an Array

LeetCode Problem 421 Difficulty: 🟡 Medium Topics: Array, Hash Table, Bit Manipulation, Trie Solution LeetCode 421 - Maximum XOR of Two Numbers in an Array Problem Understanding The problem gives us an array of non-negative integers called nums . We must choose two indices i and j such that 0 <= i <= j < n , then compute: nums[i] XOR nums[j] The goal is to return the largest XOR...

Practice › LeetCode › LeetCode 02xx ›

LeetCode 268 - Missing Number

LeetCode Problem 268 Difficulty: 🟢 Easy Topics: Array, Hash Table, Math, Binary Search, Bit Manipulation, Sorting Solution Problem Understanding The problem gives an array nums containing n distinct integers. Every number is supposed to come from the range [0, n] , which means there are actually n + 1 possible values in total. Since the array only contains n numbers, exactly one value from that range is missing. The task...

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LeetCode 136 - Single Number

LeetCode Problem 136 Difficulty: 🟢 Easy Topics: Array, Bit Manipulation Solution Problem Understanding The problem gives an integer array nums where every value appears exactly twice except for one value that appears only once. The task is to find and return that unique value. The important part of the problem is not just finding the unique number, but doing so under strict constraints. The solution must run in linear time,...

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LeetCode 779 - K-th Symbol in Grammar

LeetCode Problem 779 Difficulty: 🟡 Medium Topics: Math, Bit Manipulation, Recursion Solution Problem Understanding The problem defines a special binary grammar sequence that grows row by row. The first row contains only a single value: 0 Every later row is generated from the previous one using these rules: Replace every 0 with 01 Replace every 1 with 10 This means the rows evolve like this: Row 1: 0 Row 2:...

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LeetCode 943 - Find the Shortest Superstring

LeetCode Problem 943 Difficulty: 🔴 Hard Topics: Array, String, Dynamic Programming, Bit Manipulation, Bitmask Solution Problem Understanding The problem asks us to find the shortest superstring that contains all the given strings in the array words as substrings. In other words, we need a single string that includes every string in words at least once, concatenated in some order, but we want this superstring to have minimal length. The problem...

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LeetCode 1178 - Number of Valid Words for Each Puzzle

LeetCode Problem 1178 Difficulty: 🔴 Hard Topics: Array, Hash Table, String, Bit Manipulation, Trie Solution Problem Understanding The problem asks us to determine, for each given puzzle string, how many words from a given list words are valid for that puzzle. A word is valid for a puzzle if it contains the first character of the puzzle and all characters of the word are also present in the puzzle. The...

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LeetCode 90 - Subsets II

LeetCode Problem 90 Difficulty: 🟡 Medium Topics: Array, Backtracking, Bit Manipulation Solution Problem Understanding The problem asks us to generate every possible subset of a given integer array. A subset is any selection of elements from the array, including the empty subset and the subset containing all elements. Unlike the classic Subsets problem, this version introduces an important complication: the input array may contain duplicate values. Because of this, multiple...

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LeetCode 287 - Find the Duplicate Number

LeetCode Problem 287 Difficulty: 🟡 Medium Topics: Array, Two Pointers, Binary Search, Bit Manipulation Solution Problem Understanding The problem gives us an integer array nums of length n + 1 , where every value is guaranteed to be in the range [1, n] . Since there are n + 1 numbers but only n possible distinct values, at least one number must appear more than once. The task is to...

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LeetCode 996 - Number of Squareful Arrays

LeetCode Problem 996 Difficulty: 🔴 Hard Topics: Array, Hash Table, Math, Dynamic Programming, Backtracking, Bit Manipulation, Bitmask Solution Problem Understanding The problem asks us to count all permutations of a given integer array nums such that the array is squareful , meaning that the sum of every pair of adjacent elements is a perfect square . In other words, for a permutation [a1, a2, a3, ..., an] , each a[i]...

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LeetCode 464 - Can I Win

LeetCode Problem 464 Difficulty: 🟡 Medium Topics: Math, Dynamic Programming, Bit Manipulation, Memoization, Game Theory, Bitmask Solution LeetCode 464 - Can I Win Problem Understanding This problem describes a two-player turn-based game. Players take turns choosing a number from a shared pool of integers ranging from 1 to maxChoosableInteger . Once a number is chosen, it cannot be used again for the rest of the game. Each chosen number is...

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LeetCode 1434 - Number of Ways to Wear Different Hats to Each Other

LeetCode Problem 1434 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Bit Manipulation, Bitmask Solution LeetCode 1434 - Number of Ways to Wear Different Hats to Each Other Problem Understanding This problem asks us to count how many valid ways exist to assign hats to people under two constraints: Every person must receive exactly one hat they like. No two people may wear the same hat. The input is a 2D...

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LeetCode 137 - Single Number II

LeetCode Problem 137 Difficulty: 🟡 Medium Topics: Array, Bit Manipulation Solution Problem Understanding This problem asks us to find a unique number in an array where every other number appears exactly three times . In simpler terms, if you imagine counting all the numbers in the array, every number except one will show up three times, and our task is to identify the number that only appears once. The input...

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LeetCode 982 - Triples with Bitwise AND Equal To Zero

LeetCode Problem 982 Difficulty: 🔴 Hard Topics: Array, Hash Table, Bit Manipulation Solution Problem Understanding This problem asks us to count the number of triples (i, j, k) from an integer array nums such that the bitwise AND of the three numbers at these indices equals zero. In other words, we want all combinations where nums[i] & nums[j] & nums[k] == 0 . The input is an array of integers...

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LeetCode 1255 - Maximum Score Words Formed by Letters

LeetCode Problem 1255 Difficulty: 🔴 Hard Topics: Array, Hash Table, String, Dynamic Programming, Backtracking, Bit Manipulation, Counting, Bitmask Solution Problem Understanding This problem asks us to select a subset of words that can be constructed using a limited supply of letters, such that the total score of all chosen words is maximized. We are given three inputs: words , an array of strings letters , a multiset of available characters...

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LeetCode 810 - Chalkboard XOR Game

LeetCode Problem 810 Difficulty: 🔴 Hard Topics: Array, Math, Bit Manipulation, Brainteaser, Game Theory Solution LeetCode 810, Chalkboard XOR Game Problem Understanding This problem describes a two player game played on an array of integers. The numbers are written on a chalkboard, and players take turns erasing exactly one number. Alice moves first, then Bob, and both players play optimally. The key rule is unusual. A player loses immediately if...

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LeetCode 1595 - Minimum Cost to Connect Two Groups of Points

LeetCode Problem 1595 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Bit Manipulation, Matrix, Bitmask Solution Problem Understanding The problem is asking us to find the minimum cost to connect two groups of points, where the first group has size1 points and the second group has size2 points. We are given a cost matrix cost of size size1 x size2 where cost[i][j] represents the cost of connecting the i -th point...

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LeetCode 1461 - Check If a String Contains All Binary Codes of Size K

LeetCode Problem 1461 Difficulty: 🟡 Medium Topics: Hash Table, String, Bit Manipulation, Rolling Hash, Hash Function Solution Problem Understanding The problem gives us a binary string s and an integer k . A binary string contains only the characters '0' and '1' . We must determine whether every possible binary code of length k appears somewhere inside s as a substring. A binary code of length k is simply any...

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LeetCode 762 - Prime Number of Set Bits in Binary Representation

LeetCode Problem 762 Difficulty: 🟢 Easy Topics: Math, Bit Manipulation Solution Problem Understanding The problem requires counting the numbers within a given inclusive range [left, right] that have a prime number of set bits in their binary representation. The set bits of a number refer to the number of 1 s in its binary representation. For example, the number 6 in binary is 110 , which has 2 set bits....

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LeetCode 1356 - Sort Integers by The Number of 1 Bits

LeetCode Problem 1356 Difficulty: 🟢 Easy Topics: Array, Bit Manipulation, Sorting, Counting Solution Problem Understanding The problem asks us to sort an integer array arr based on the number of 1 bits in the binary representation of each element. This means that we are not sorting by the integer value itself but by the count of 1 s in its binary form. If two numbers have the same number of...

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LeetCode 980 - Unique Paths III

LeetCode Problem 980 Difficulty: 🔴 Hard Topics: Array, Backtracking, Bit Manipulation, Matrix Solution Problem Understanding This problem asks us to count the number of valid paths in a grid under very strict movement rules. We are given a matrix where each cell has a special meaning: 1 is the starting position 2 is the ending position 0 is an empty square we may walk on -1 is an obstacle that...

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LeetCode 389 - Find the Difference

LeetCode Problem 389 Difficulty: 🟢 Easy Topics: Hash Table, String, Bit Manipulation, Sorting Solution Problem Understanding This problem gives us two strings, s and t . The string t is created by taking all characters from s , shuffling them into a different order, and then inserting exactly one additional character somewhere in the string. Our task is to identify and return that extra character. In other words, every character...

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LeetCode 1457 - Pseudo-Palindromic Paths in a Binary Tree

LeetCode Problem 1457 Difficulty: 🟡 Medium Topics: Bit Manipulation, Tree, Depth-First Search, Breadth-First Search, Binary Tree Solution Problem Understanding This problem asks us to count how many root to leaf paths in a binary tree are "pseudo-palindromic". A palindrome is a sequence that reads the same forward and backward. For example, [1,2,1] and [3,4,4,3] are palindromes. The important property of a palindrome is that at most one value may appear...

Practice › LeetCode › LeetCode 13xx ›

LeetCode 1310 - XOR Queries of a Subarray

LeetCode Problem 1310 Difficulty: 🟡 Medium Topics: Array, Bit Manipulation, Prefix Sum Solution You asked for the complete guide in a single response, but your previous message includes two separate LeetCode problems with full long form requirements: LeetCode 1305 - All Elements in Two Binary Search Trees LeetCode 1310 - XOR Queries of a Subarray A complete reference quality guide for even one problem, with all required sections, detailed prose,...

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LeetCode 1611 - Minimum One Bit Operations to Make Integers Zero

LeetCode Problem 1611 Difficulty: 🔴 Hard Topics: Math, Dynamic Programming, Bit Manipulation, Recursion, Memoization Solution Problem Understanding This problem asks us to transform a given integer n into 0 using a specialized set of bit-flipping operations. Each operation allows you to flip either the rightmost bit of the binary representation of n , or the i-th bit if the (i-1)-th bit is set to 1 and all lower bits (i-2...

Practice › LeetCode › LeetCode 04xx ›

LeetCode 477 - Total Hamming Distance

LeetCode Problem 477 Difficulty: 🟡 Medium Topics: Array, Math, Bit Manipulation Solution Problem Understanding The problem asks us to compute the total Hamming distance between every possible pair of integers in the array. The Hamming distance between two integers is defined as the number of bit positions where the two numbers differ. For example: 4 = 0100 14 = 1110 Comparing the bits position by position: Bit Position 4 14...

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LeetCode 405 - Convert a Number to Hexadecimal

LeetCode Problem 405 Difficulty: 🟢 Easy Topics: Math, String, Bit Manipulation Solution Problem Understanding The problem asks us to convert a given 32-bit integer num into its hexadecimal representation as a string. Hexadecimal, or base-16, uses digits 0-9 and letters a-f to represent values 0-15 . For positive numbers, the conversion is straightforward: repeatedly divide the number by 16 and map remainders to the hexadecimal digits. For negative numbers, the...

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LeetCode 1016 - Binary String With Substrings Representing 1 To N

LeetCode Problem 1016 Difficulty: 🟡 Medium Topics: Hash Table, String, Bit Manipulation, Sliding Window Solution Problem Understanding The problem asks us to determine whether a given binary string s contains all binary representations of integers from 1 to n as substrings . In other words, for every integer i such that 1 <= i <= n , if you convert i to its binary form, that binary string must appear...

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LeetCode 260 - Single Number III

LeetCode Problem 260 Difficulty: 🟡 Medium Topics: Array, Bit Manipulation Solution Problem Understanding The problem gives an integer array nums where every value appears exactly twice, except for two numbers that appear only once. The task is to find those two unique numbers and return them in any order. In other words, the array mostly contains duplicate pairs, but there are exactly two elements that do not have matching duplicates....

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LeetCode 2035 - Partition Array Into Two Arrays to Minimize Sum Difference

LeetCode Problem 2035 Difficulty: 🔴 Hard Topics: Array, Two Pointers, Binary Search, Dynamic Programming, Bit Manipulation, Sorting, Ordered Set, Bitmask Solution Problem Understanding The problem gives an array nums containing exactly 2 * n integers. We must divide these integers into two separate groups, each containing exactly n elements. After forming the two groups, we compute the sum of each group and measure the absolute difference between those sums. Our...

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LeetCode 78 - Subsets

LeetCode Problem 78 Difficulty: 🟡 Medium Topics: Array, Backtracking, Bit Manipulation Solution LeetCode 78, Subsets Problem Understanding This problem asks us to generate every possible subset of a given array of unique integers. A subset is any selection of elements from the array, including the empty subset and the subset containing every element. If the input array has n elements, then there are exactly 2^n possible subsets. This comes from...

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LeetCode 29 - Divide Two Integers

LeetCode Problem 29 Difficulty: 🟡 Medium Topics: Math, Bit Manipulation Solution Problem Understanding The problem asks us to implement integer division without using the standard arithmetic operators for multiplication, division, or modulo. We are given two integers, dividend and divisor , and we must compute the quotient obtained by dividing the dividend by the divisor. The result must follow truncation toward zero. This means that any fractional portion is discarded...

Practice › LeetCode › LeetCode 06xx ›

LeetCode 693 - Binary Number with Alternating Bits

LeetCode Problem 693 Difficulty: 🟢 Easy Topics: Bit Manipulation Solution Problem Understanding The problem asks us to determine whether the binary representation of a given positive integer n has alternating bits. In other words, for the binary digits of n , no two consecutive bits should be the same. For example, 101 is alternating, while 111 is not because it contains consecutive ones. The input n is guaranteed to be...

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LeetCode 1349 - Maximum Students Taking Exam

LeetCode Problem 1349 Difficulty: 🔴 Hard Topics: Array, Dynamic Programming, Bit Manipulation, Matrix, Bitmask Solution LeetCode 1349 is long and detailed enough that a complete high quality guide with all required sections, full prose explanations, worked examples, corrected Python and Go implementations, exhaustive test cases, and edge case analysis will exceed a single response limit if done properly. I can provide the full reference-quality guide in consecutive parts , while...

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LeetCode 318 - Maximum Product of Word Lengths

LeetCode Problem 318 Difficulty: 🟡 Medium Topics: Array, String, Bit Manipulation Solution LeetCode 318 - Maximum Product of Word Lengths Problem Understanding The problem gives us an array of lowercase English words. We need to find two different words such that they do not share any common letters, then return the maximum possible product of their lengths. More formally, for every pair of indices (i, j) where i != j...

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LeetCode 1342 - Number of Steps to Reduce a Number to Zero

LeetCode Problem 1342 Difficulty: 🟢 Easy Topics: Math, Bit Manipulation Solution LeetCode 1342, Number of Steps to Reduce a Number to Zero Problem Understanding The problem gives us a non-negative integer num and asks us to compute how many operations are required to reduce it all the way down to 0 . At every step, we apply one of two rules: If the current number is even, divide it by...

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LeetCode 1238 - Circular Permutation in Binary Representation

LeetCode Problem 1238 Difficulty: 🟡 Medium Topics: Math, Backtracking, Bit Manipulation Solution LeetCode 1238 - Circular Permutation in Binary Representation Problem Understanding This problem asks us to construct a special ordering of all integers from 0 to 2^n - 1 . The ordering must satisfy the properties of a circular Gray code sequence. We are given two integers: n , which determines how many numbers exist in the permutation start...

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LeetCode 1483 - Kth Ancestor of a Tree Node

LeetCode Problem 1483 Difficulty: 🔴 Hard Topics: Binary Search, Dynamic Programming, Bit Manipulation, Tree, Depth-First Search, Breadth-First Search, Design Solution Problem Understanding The problem gives us a rooted tree with n nodes labeled from 0 to n - 1 . Instead of providing the tree as adjacency lists or edges, the input is represented using a parent array. For every node i , parent[i] tells us which node is its...

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LeetCode 201 - Bitwise AND of Numbers Range

LeetCode Problem 201 Difficulty: 🟡 Medium Topics: Bit Manipulation Solution Problem Understanding The problem asks us to compute the bitwise AND of every integer in the inclusive range [left, right] . For example, if left = 5 and right = 7 , the numbers in the range are: 5 = 101 6 = 110 7 = 111 Applying bitwise AND across all values: 101 110 111 --- 100 = 4...

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LeetCode 190 - Reverse Bits

LeetCode Problem 190 Difficulty: 🟢 Easy Topics: Divide and Conquer, Bit Manipulation Solution Problem Understanding The problem asks us to reverse the binary representation of a 32-bit integer . Instead of reversing the decimal digits of a number, we reverse the order of its individual bits. For example, suppose the binary representation of a number is: 00000010100101000001111010011100 After reversing all 32 bits, it becomes: 00111001011110000010100101000000 The resulting reversed binary value...

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LeetCode 191 - Number of 1 Bits

LeetCode Problem 191 Difficulty: 🟢 Easy Topics: Divide and Conquer, Bit Manipulation Solution Problem Understanding The problem asks us to count how many bits are set to 1 in the binary representation of a positive integer n . A set bit is simply a bit whose value is 1 . For example, the number 11 in binary is: 1011 This binary representation contains three 1 bits, so the answer is...

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LeetCode 1009: Complement of Base 10 Integer

Problem Restatement The complement of an integer is obtained by flipping all its bits. For example, the decimal number 5 is 101 in binary. Its complement is 010 , which is 2 . We are given an integer n and need to return its complement. Note: the complement does not flip leading zeros (only the bits in the binary representation of n count). The official constraints state that 0 <=...

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LeetCode 1018: Binary Prefix Divisible By 5

Problem Restatement We are given a binary array nums . For each index i , consider the binary number formed by nums[0], nums[1], ..., nums[i] . We need to return a boolean array answer where answer[i] is true if the binary number formed by the prefix nums[0:i+1] is divisible by 5 . The official constraints state that 1 <= nums.length <= 10^5 and nums[i] is either 0 or 1 ....

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LeetCode 1066: Campus Bikes II

Problem Restatement We have n workers and m bikes on a campus. We need to assign each worker exactly one bike, minimizing the total Manhattan distance between each worker and their assigned bike. Return the minimum total Manhattan distance. The official constraints state that n <= m <= 10 (small, bitmask DP is feasible). Input and Output Item Meaning Input Worker positions and bike positions Output Minimum total assignment distance...

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LeetCode 898: Bitwise ORs of Subarrays

Problem Restatement We are given an integer array arr . For every non-empty contiguous subarray, compute the bitwise OR of all elements in that subarray. Return the number of distinct OR results. A subarray must be contiguous. The official constraints allow arr.length <= 5 * 10^4 and arr[i] <= 10^9 . ( leetcode.com ) Input and Output Item Meaning Input arr , an integer array Output Number of distinct bitwise...

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LeetCode 995: Minimum Number of K Consecutive Bit Flips

Problem Restatement We are given a binary array nums and an integer k . A k -bit flip means choosing a contiguous subarray of length k and flipping every bit in it: Bit After flip 0 1 1 0 We need to return the minimum number of k -bit flips required so that the array contains no 0 . If it is impossible, return -1 . The official problem defines...

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LeetCode 868: Binary Gap

Problem Restatement We are given a positive integer n . Write n in binary form. We need to find the maximum distance between two adjacent 1 bits. The distance between two bits is the absolute difference between their positions. Only adjacent 1 bits matter. Input and Output Item Meaning Input Positive integer n Output Maximum distance between adjacent 1 bits in binary Adjacent 1 s Consecutive 1 bits when scanning...

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LeetCode 717: 1-bit and 2-bit Characters

Problem Restatement We are given a binary array: bits The array encodes characters using two rules: Character Type Encoding One-bit character 0 Two-bit character 10 or 11 The array always ends with: 0 We need to determine whether the final character must be a one-bit character. Return: True if the last character is one-bit. Otherwise return: False Input and Output Item Meaning Input Binary array bits Output Whether the last...

Practice › LeetCode › LeetCode (archived) › LeetCode 07xx ›

LeetCode 762: Prime Number of Set Bits in Binary Representation

Problem Restatement We are given two integers: left right We need to count how many integers x in the inclusive range: left <= x <= right have a prime number of set bits in their binary representation. A set bit is a bit equal to 1 . For example: 21 = 10101 The binary representation of 21 has three 1 bits. Since 3 is prime, 21 should be counted. Also,...

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LeetCode 861: Score After Flipping Matrix

Problem Restatement We are given a binary matrix grid . We may perform any number of operations. Each operation can: Flip one row Flip one column Flipping means changing: 0 -> 1 1 -> 0 After all operations, every row is interpreted as a binary number. The total score is the sum of those binary numbers. We need to return the largest possible score. Input and Output Item Meaning Input...

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LeetCode 810: Chalkboard XOR Game

Problem Restatement We are given an array nums of non-negative integers written on a chalkboard. Alice and Bob take turns erasing exactly one number. Alice moves first. After a player erases a number, if the XOR of all remaining numbers becomes 0 , that player loses. There is one special rule: if a player starts their turn and the XOR of all numbers is already 0 , that player wins...

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LeetCode 693: Binary Number with Alternating Bits

Problem Restatement We are given a positive integer n . We need to check whether its binary representation has alternating bits. That means every pair of adjacent bits must be different. The official statement says two adjacent bits should always have different values. For example, 5 is valid because its binary representation is 101 , while 7 is invalid because its binary representation is 111 . Input and Output Item...

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LeetCode 672: Bulb Switcher II

Problem Restatement There are n bulbs labeled from 1 to n . All bulbs are initially on. There are four buttons: Button Operation Button 1 Flip all bulbs Button 2 Flip bulbs with even labels Button 3 Flip bulbs with odd labels Button 4 Flip bulbs with labels 3k + 1 , such as 1, 4, 7, 10, ... We must press buttons exactly presses times. For each press, we...

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LeetCode 832: Flipping an Image

Problem Restatement We are given an n x n binary matrix image . Each cell is either: Value Meaning 0 White pixel 1 Black pixel We need to do two operations: Flip the image horizontally. Invert the image. Flipping horizontally means reversing each row. For example: [1, 1, 0] -> [0, 1, 1] Inverting means changing every 0 to 1 and every 1 to 0 . For example: [0, 1,...

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LeetCode 982: Triples with Bitwise AND Equal To Zero

Problem Restatement We are given an integer array nums . We need to count the number of ordered triples of indices (i, j, k) such that: nums[i] & nums[j] & nums[k] == 0 The indices may repeat. For example, (0, 0, 1) is allowed. The triple is ordered, so (0, 1, 2) and (1, 0, 2) are counted as different triples if both satisfy the condition. The official constraints are:...

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LeetCode 782: Transform to Chessboard

Problem Restatement We are given an n x n binary board. Each cell is either 0 or 1 . In one move, we may do one of these operations: Move Meaning Swap two rows Exchange any two complete rows Swap two columns Exchange any two complete columns We need to return the minimum number of moves required to transform the board into a chessboard. A chessboard means no two 4-directionally...

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LeetCode 779: K-th Symbol in Grammar

Problem Restatement We build a table of rows. The first row is: 0 To build the next row, every symbol is replaced: Symbol Becomes 0 01 1 10 So the first few rows are: row 1: 0 row 2: 01 row 3: 0110 row 4: 01101001 Given integers n and k , return the k -th symbol in row n . The position k is 1-indexed. Input and Output Item...

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LeetCode 600: Non-negative Integers without Consecutive Ones

Problem Restatement We are given a positive integer n . We need to count how many integers in the range [0, n] have binary representations that do not contain consecutive 1 bits. For example, 3 has binary representation: 11 so it is invalid. But 5 has binary representation: 101 so it is valid. Return the count of valid integers from 0 through n , inclusive. The official problem asks for...

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LeetCode 751: IP to CIDR

Problem Restatement We are given a starting IPv4 address ip and an integer n . We need to cover exactly n consecutive IP addresses starting from ip . The answer should be a list of CIDR blocks with the smallest possible length. A CIDR block looks like this: "123.45.67.89/20" The number after / is the prefix length. A larger prefix length means a smaller block. For example, /32 covers exactly...

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LeetCode 421: Maximum XOR of Two Numbers in an Array

Problem Restatement We are given an integer array nums . Return the maximum value of: nums[i] ^ nums[j] where ^ means bitwise XOR. The indices may be the same according to the source statement: 0 <= i <= j < n Using the same element gives XOR value 0 , so it never hurts the maximum when there are at least two useful values. The source constraints are: 1 <=...

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LeetCode 397: Integer Replacement

Problem Restatement We are given a positive integer n . We need to turn n into 1 using the fewest operations. The allowed operations are: Case Operation n is even Replace n with n / 2 n is odd Replace n with either n + 1 or n - 1 Return the minimum number of operations needed. For example: n = 8 The best path is: 8 -> 4 ->...

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LeetCode 371: Sum of Two Integers

Problem Restatement Given two integers a and b , return their sum without using the + or - operators. The problem is asking us to implement integer addition using bit operations. The official statement gives examples such as a = 1, b = 2 , with output 3 . Input and Output Item Meaning Input Two integers a and b Output The integer sum of a and b Restriction Do...

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LeetCode 320: Generalized Abbreviation

Problem Restatement We are given a lowercase string word . Return all possible generalized abbreviations of word . A generalized abbreviation replaces any number of non-overlapping and non-adjacent substrings with their lengths. For example, "abcde" can become "a3e" , "1bcd1" , "5" , or "abcde" . The input length is at most 15 , and the answer can be returned in any order. Input and Output Item Meaning Input A...

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LeetCode 318: Maximum Product of Word Lengths

Problem Restatement We are given an array of lowercase strings words . Return the maximum value of: len(words[i]) * len(words[j]) where the two words do not share any common letters. If no such pair exists, return 0 . The official constraints include 2 <= words.length <= 1000 , 1 <= words[i].length <= 1000 , and each word contains only lowercase English letters. Input and Output Item Meaning Input A list...

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LeetCode 393: UTF-8 Validation

Problem Restatement We are given an integer array data . Each integer represents one byte of data. Only the least significant 8 bits are used. We need to decide whether this byte sequence is a valid UTF-8 encoding. A UTF-8 character can be 1 to 4 bytes long. The valid byte patterns are: Number of bytes Pattern 1 byte 0xxxxxxx 2 bytes 110xxxxx 10xxxxxx 3 bytes 1110xxxx 10xxxxxx 10xxxxxx 4...

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LeetCode 268: Missing Number

Problem Restatement We are given an array nums containing n distinct numbers from the range: 0, 1, 2, ..., n Exactly one number from this range is missing. Return the missing number. For example, if: nums = [3, 0, 1] then n = 3 , so the full range should be: [0, 1, 2, 3] The missing number is: 2 The problem asks for an algorithm with linear runtime. The...

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LeetCode 90: Subsets II

Problem Restatement We are given an integer array nums . Unlike LeetCode 78, this array may contain duplicate values. We need to return all possible subsets, also called the power set. The answer must not contain duplicate subsets. The subsets may be returned in any order. The official statement says that nums may contain duplicates, the solution set must not contain duplicate subsets, and the constraints are 1 <= nums.length...

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LeetCode 191: Number of 1 Bits

Problem Restatement We are given a positive integer n . We need to return the number of 1 bits in its binary representation. This count is also called the Hamming weight. The official problem asks for the number of set bits in the binary representation of n . A set bit means a bit whose value is 1 . For example: n = 11 binary = 1011 There are three...

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LeetCode 89: Gray Code

Problem Restatement We are given an integer n . We need to return any valid n -bit Gray code sequence. A valid Gray code sequence has these rules: Rule Meaning Length The sequence contains 2^n integers Range Every integer is between 0 and 2^n - 1 Start The first integer must be 0 No duplicates Each integer appears at most once Adjacent rule Adjacent integers differ by exactly one bit...

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LeetCode 190: Reverse Bits

Problem Restatement We are given a 32-bit integer n . We need to reverse its 32 bits and return the integer represented by the reversed bit pattern. The official statement asks us to reverse the bits of a given 32-bit integer. For example, the binary form of 43261596 is: 00000010100101000001111010011100 After reversing all 32 bits, we get: 00111001011110000010100101000000 That binary value is 964176192 . Input and Output Item Meaning Input...

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LeetCode 389: Find the Difference

Problem Restatement We are given two strings s and t . String t is created by shuffling s and adding one extra letter at a random position. We need to return the added letter. For example: s = "abcd" t = "abcde" The added letter is: "e" The strings contain only lowercase English letters. Also, t always has exactly one more character than s . Input and Output Item Meaning...

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LeetCode 137: Single Number II

Problem Restatement We are given an integer array nums . Every element appears exactly three times except for one element, which appears exactly once. Return the element that appears once. The solution must run in linear time and use constant extra space. LeetCode explicitly requires this. Examples Example 1: nums = [2, 2, 3, 2] The number 2 appears three times. The number 3 appears once. Output: 3 Example 2:...

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LeetCode 411: Minimum Unique Word Abbreviation

Problem Restatement We are given a target string and a dictionary of strings. We need to find the shortest abbreviation of target that does not conflict with any abbreviation of any word in the dictionary. An abbreviation may replace substrings with their lengths. Each number or letter in the abbreviation counts as length 1 . For example, "a32bc" has abbreviation length 4 . If multiple shortest answers exist, any one...

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LeetCode 342: Power of Four

Problem Restatement We are given an integer n . Return true if n is a power of four. Otherwise return false . A number is a power of four if there exists an integer x such that: n = 4^x Examples: 1 = 4^0 4 = 4^1 16 = 4^2 64 = 4^3 are powers of four. The official problem asks whether n is a power of four and includes...

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LeetCode 136: Single Number

Problem Restatement We are given a non-empty integer array nums . Every element appears exactly twice except for one element. We need to return the element that appears only once. The solution must run in linear time and use constant extra space. LeetCode states this explicitly in the problem requirements. Examples Example 1: nums = [2, 2, 1] The number 2 appears twice. The number 1 appears once. Output: 1...

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LeetCode 461: Hamming Distance

Problem Restatement We are given two integers x and y . We need to return the Hamming distance between them. For two integers, the Hamming distance is the number of bit positions where their binary representations are different. The official problem asks us to return the Hamming distance between two integers x and y . For example: x = 1 y = 4 Their binary forms are: 1 = 0001...

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LeetCode 338: Counting Bits

Problem Restatement We are given an integer n . Return an array ans of length n + 1 . For every integer i from 0 to n , ans[i] should be the number of 1 bits in the binary representation of i . The official problem asks for this array for all values 0 <= i <= n . For example: n = 5 The binary forms are: 0 ->...

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LeetCode 260: Single Number III

Problem Restatement We are given an integer array nums . Exactly two numbers appear only once. Every other number appears exactly twice. We need to return the two numbers that appear only once. The answer may be returned in any order. The problem asks for: Linear runtime Constant extra space The constraints are 2 <= nums.length <= 3 * 10^4 , -2^31 <= nums[i] <= 2^31 - 1 . Input...

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LeetCode 231: Power of Two

Problem Restatement We are given an integer n . We need to determine whether n is a power of two. That means we must check whether there exists an integer x such that: $$ n = 2^x $$ where: x >= 0 Examples of powers of two: 1 = 2^0 2 = 2^1 4 = 2^2 8 = 2^3 16 = 2^4 Examples that are not powers of two: 3...

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LeetCode 405: Convert a Number to Hexadecimal

Problem Restatement We are given a 32-bit signed integer num . We must return its hexadecimal representation as a lowercase string. The hexadecimal digits are: 0 1 2 3 4 5 6 7 8 9 a b c d e f We must not use built-in conversion functions such as: hex() Negative numbers use two's complement representation. If the number is 0 , return: "0" Input and Output Item Meaning...

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LeetCode 29: Divide Two Integers

Problem Restatement We are given two integers, dividend and divisor . We need to compute the integer quotient of: dividend / divisor But we cannot use multiplication, division, or modulo operators. The result should truncate toward zero. That means we remove the fractional part. Examples: 10 / 3 = 3.333... -> 3 7 / -3 = -2.333... -> -2 The answer must stay inside the 32-bit signed integer range: [-2^31,...

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LeetCode 78: Subsets

Problem Restatement We are given an integer array nums . Every element in nums is unique. We need to return all possible subsets of nums . A subset may contain: Size Meaning 0 elements The empty subset [] Some elements Any valid partial selection All elements The whole array The answer must not contain duplicate subsets. The subsets may be returned in any order. The official problem states that nums...

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LeetCode 477: Total Hamming Distance

Problem Restatement We are given an integer array nums . The Hamming distance between two integers is the number of bit positions where their binary representations are different. We need to return the sum of Hamming distances over all pairs of integers in nums . For example: nums = [4, 14, 2] Their binary forms are: 4 = 0100 14 = 1110 2 = 0010 Pair distances: HammingDistance(4, 14) =...

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LeetCode 476: Number Complement

Problem Restatement We are given a positive integer num . We need to flip every bit in its binary representation: Bit After flip 0 1 1 0 Then we return the decimal value of the flipped binary number. For example, 5 in binary is: 101 After flipping every bit: 010 010 in binary is 2 , so the answer is 2 . The problem uses the normal binary representation without...

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LeetCode 401: Binary Watch

Problem Restatement A binary watch uses LEDs to show time. There are 4 LEDs for the hour. The hour range is: 0 <= hour <= 11 There are 6 LEDs for the minute. The minute range is: 0 <= minute <= 59 Each LED represents one binary bit. A bit with value 1 means the LED is on. Given an integer turnedOn , return all possible valid times where exactly...

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LeetCode 201: Bitwise AND of Numbers Range

Problem Restatement We are given two integers left and right . They define an inclusive range: [left, left + 1, left + 2, ..., right] We need to return the bitwise AND of every number in that range. The official statement says: given two integers left and right representing the range [left, right] , return the bitwise AND of all numbers in this range, inclusive. The constraints are 0 <=...

#bit-manipulation

LeetCode 3158 - Find the XOR of Numbers Which Appear Twice

LeetCode 3670 - Maximum Product of Two Integers With No Common Bits

LeetCode 3621 - Number of Integers With Popcount-Depth Equal to K I

LeetCode 3615 - Longest Palindromic Path in Graph

LeetCode 3644 - Maximum K to Sort a Permutation

LeetCode 3882 - Minimum XOR Path in a Grid

LeetCode 3878 - Count Good Subarrays

LeetCode 3877 - Minimum Removals to Achieve Target XOR

LeetCode 3858 - Minimum Bitwise OR From Grid

LeetCode 3766 - Minimum Operations to Make Binary Palindrome

LeetCode 3757 - Number of Effective Subsequences

LeetCode 3845 - Maximum Subarray XOR with Bounded Range

LeetCode 3750 - Minimum Number of Flips to Reverse Binary String

LeetCode 3827 - Count Monobit Integers

LeetCode 3825 - Longest Strictly Increasing Subsequence With Non-Zero Bitwise AND

LeetCode 3821 - Find Nth Smallest Integer With K One Bits

LeetCode 3811 - Number of Alternating XOR Partitions

LeetCode 3806 - Maximum Bitwise AND After Increment Operations

LeetCode 3702 - Longest Subsequence With Non-Zero Bitwise XOR

LeetCode 3801 - Minimum Cost to Merge Sorted Lists

LeetCode 3755 - Find Maximum Balanced XOR Subarray Length

LeetCode 3681 - Maximum XOR of Subsequences

LeetCode 3568 - Minimum Moves to Clean the Classroom

LeetCode 3595 - Once Twice

LeetCode 3566 - Partition Array into Two Equal Product Subsets

LeetCode 3539 - Find Sum of Array Product of Magical Sequences

LeetCode 3534 - Path Existence Queries in a Graph II

LeetCode 3495 - Minimum Operations to Make Array Elements Zero

LeetCode 3688 - Bitwise OR of Even Numbers in an Array

LeetCode 3677 - Count Binary Palindromic Numbers

LeetCode 3674 - Minimum Operations to Equalize Array

LeetCode 3646 - Next Special Palindrome Number

LeetCode 3632 - Subarrays with XOR at Least K

LeetCode 3630 - Partition Array for Maximum XOR and AND

LeetCode 3599 - Partition Array to Minimize XOR

LeetCode 3594 - Minimum Time to Transport All Individuals

LeetCode 3585 - Find Weighted Median Node in Tree

LeetCode 3559 - Number of Ways to Assign Edge Weights II

LeetCode 3553 - Minimum Weighted Subgraph With the Required Paths II

LeetCode 3533 - Concatenated Divisibility

LeetCode 3530 - Maximum Profit from Valid Topological Order in DAG

LeetCode 3514 - Number of Unique XOR Triplets II

LeetCode 3513 - Number of Unique XOR Triplets I

LeetCode 3444 - Minimum Increments for Target Multiples in an Array

LeetCode 3435 - Frequencies of Shortest Supersequences

LeetCode 3376 - Minimum Time to Break Locks I

LeetCode 3108 - Minimum Cost Walk in Weighted Graph

LeetCode 2527 - Find Xor-Beauty of Array

LeetCode 3191 - Minimum Operations to Make Binary Array Elements Equal to One I

LeetCode 1787 - Make the XOR of All Segments Equal to Zero

LeetCode 2749 - Minimum Operations to Make the Integer Zero

LeetCode 3315 - Construct the Minimum Bitwise Array II

LeetCode 2680 - Maximum OR

LeetCode 3133 - Minimum Array End

LeetCode 2546 - Apply Bitwise Operations to Make Strings Equal

LeetCode 1947 - Maximum Compatibility Score Sum

LeetCode 2568 - Minimum Impossible OR

LeetCode 2846 - Minimum Edge Weight Equilibrium Queries in a Tree

LeetCode 3283 - Maximum Number of Moves to Kill All Pawns

LeetCode 1908 - Game of Nim

LeetCode 1994 - The Number of Good Subsets

LeetCode 2206 - Divide Array Into Equal Pairs

LeetCode 2917 - Find the K-or of an Array

LeetCode 2128 - Remove All Ones With Row and Column Flips

LeetCode 2857 - Count Pairs of Points With Distance k

LeetCode 2571 - Minimum Operations to Reduce an Integer to 0

LeetCode 2939 - Maximum Xor Product

LeetCode 3215 - Count Triplets with Even XOR Set Bits II

LeetCode 2419 - Longest Subarray With Maximum Bitwise AND

LeetCode 3097 - Shortest Subarray With OR at Least K II

LeetCode 3304 - Find the K-th Character in String Game I

LeetCode 2157 - Groups of Strings

LeetCode 2959 - Number of Possible Sets of Closing Branches

LeetCode 3068 - Find the Maximum Sum of Node Values

LeetCode 2506 - Count Pairs Of Similar Strings

LeetCode 2247 - Maximum Cost of Trip With K Highways

LeetCode 2220 - Minimum Bit Flips to Convert Number

LeetCode 3094 - Guess the Number Using Bitwise Questions II

LeetCode 2836 - Maximize Value of Function in a Ball Passing Game