tag

#quickselect

14 pages tagged

Practice › LeetCode › LeetCode 37xx ›

LeetCode 3759 - Count Elements With at Least K Greater Values

LeetCode Problem 3759 Difficulty: 🟡 Medium Topics: Array, Binary Search, Divide and Conquer, Sorting, Quickselect Solution Problem Understanding The problem asks us to count how many elements in an array have at least k values that are strictly greater than them. More concretely, for every element nums[i] , we need to determine how many numbers in the array are larger than nums[i] . If that count is at least k...
leetcode Medium array binary-search divide-and-conquer sorting quickselect May 30, 2026
Practice › LeetCode › LeetCode 19xx ›

LeetCode 1985 - Find the Kth Largest Integer in the Array

LeetCode Problem 1985 Difficulty: 🟡 Medium Topics: Array, String, Divide and Conquer, Sorting, Heap (Priority Queue), Quickselect Solution Problem Understanding This problem asks us to find the kth largest value among a list of integers that are represented as strings. Each element in nums is a non-negative integer encoded as a string with no leading zeros, and we are required to return the kth largest value according to numeric order,...
leetcode Medium array string divide-and-conquer sorting heap-(priority-queue) quickselect May 29, 2026
Practice › LeetCode › LeetCode 23xx ›

LeetCode 2343 - Query Kth Smallest Trimmed Number

LeetCode Problem 2343 Difficulty: 🟡 Medium Topics: Array, String, Divide and Conquer, Sorting, Heap (Priority Queue), Radix Sort, Quickselect Solution Problem Understanding This problem provides a list of numbers represented as strings, all of equal length. The task is to answer multiple queries, where each query asks for the index of the k-th smallest number after trimming every number in the list to its last trimi digits. Importantly, if two...
leetcode Medium array string divide-and-conquer sorting heap-(priority-queue) radix-sort quickselect May 29, 2026
Practice › LeetCode › LeetCode 03xx ›

LeetCode 324 - Wiggle Sort II

LeetCode Problem 324 Difficulty: 🟡 Medium Topics: Array, Divide and Conquer, Greedy, Sorting, Quickselect Solution Problem Understanding The problem asks us to rearrange an array so that it follows a strict alternating pattern: nums[0] < nums[1] nums[1] > nums[2] nums[2] < nums[3] and so on. This pattern is called a wiggle sequence because the values repeatedly go up and down. The input is an integer array nums , and we...
leetcode Medium array divide-and-conquer greedy sorting quickselect May 28, 2026
Practice › LeetCode › LeetCode 02xx ›

LeetCode 215 - Kth Largest Element in an Array

LeetCode Problem 215 Difficulty: 🟡 Medium Topics: Array, Divide and Conquer, Sorting, Heap (Priority Queue), Quickselect Solution Problem Understanding The problem asks us to find the kth largest element in an unsorted integer array. The important detail is that we are looking for the element that would appear in the kth position if the array were sorted in descending order. We are not looking for the kth distinct value. For...
leetcode Medium array divide-and-conquer sorting heap-(priority-queue) quickselect May 28, 2026
Practice › LeetCode › LeetCode 09xx ›

LeetCode 973 - K Closest Points to Origin

LeetCode Problem 973 Difficulty: 🟡 Medium Topics: Array, Math, Divide and Conquer, Geometry, Sorting, Heap (Priority Queue), Quickselect Solution Problem Understanding This problem asks us to find the k points that are closest to the origin (0,0) from a list of 2D points. Each point is given as a pair [x, y] , and the distance is defined using the Euclidean formula, sqrt(x^2 + y^2) . The input consists of...
leetcode Medium array math divide-and-conquer geometry sorting heap-(priority-queue) quickselect May 28, 2026
Practice › LeetCode › LeetCode 03xx ›

LeetCode 347 - Top K Frequent Elements

LeetCode Problem 347 Difficulty: 🟡 Medium Topics: Array, Hash Table, Divide and Conquer, Sorting, Heap (Priority Queue), Bucket Sort, Counting, Quickselect Solution Problem Understanding The problem asks us to return the k most frequently occurring elements from an integer array. We are given an array nums , which may contain duplicates, and an integer k . Our task is to identify which values appear most often and return exactly k...
leetcode Medium array hash-table divide-and-conquer sorting heap-(priority-queue) bucket-sort counting quickselect May 28, 2026
Practice › LeetCode › LeetCode 17xx ›

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...
leetcode Medium array divide-and-conquer bit-manipulation sorting heap-(priority-queue) matrix prefix-sum quickselect May 28, 2026
Practice › LeetCode › LeetCode (archived) › LeetCode 03xx ›

LeetCode 324: Wiggle Sort II

Problem Restatement We are given an integer array nums . Rearrange it in-place so that: nums[0] < nums[1] > nums[2] < nums[3] ... This alternating pattern is called wiggle order. The official problem guarantees that a valid answer exists. The follow-up asks for O(n) average time and O(1) extra space. Input and Output Item Meaning Input Integer array nums Output Rearrange nums in-place Wiggle rule nums[0] < nums[1] > nums[2]...
leetcode array sorting greedy quickselect May 10, 2026
Practice › LeetCode › LeetCode (archived) › LeetCode 02xx ›

LeetCode 215: Kth Largest Element in an Array

Problem Restatement We are given an integer array nums and an integer k . We need to return the k th largest element in the array. Important detail: this means the k th largest element in sorted order, not the k th distinct element. Duplicates count separately. The official constraints are 1 <= k <= nums.length <= 10^5 and -10^4 <= nums[i] <= 10^4 . Input and Output Item Meaning...
leetcode array heap quickselect divide-and-conquer May 10, 2026
Programming › Algorithm Cookbook › Chapter 6. Sorting ›

6.13 Quickselect

6.13 Quickselect Quickselect finds the element that would appear at a given index if the array were sorted. It uses the same partitioning idea as quick sort, but it recurses into only one side. This makes it useful for medians, percentiles, and top k boundaries. Problem You have an array A[0..n-1] and an index k . You want the element with rank k , using zero-based indexing, without fully sorting...
algorithms sorting quickselect selection May 4, 2026
Wiki › Algorithms › 01. Searching and Sorting › 5. Selection and Order Statistics ›

Randomized Quickselect

Randomized Quickselect Randomized Quickselect improves Quickselect by choosing the pivot uniformly at random. This removes dependence on input order and avoids pathological worst cases in practice. The structure remains identical to Quickselect. Only pivot selection changes. Problem Given an array $A$ of length $n$ and an integer $k$ with $0 \le k < n$, return the k-th smallest element. Algorithm At each step, select a random pivot, partition, and recurse...
algorithms selection randomized quickselect
Wiki › Algorithms › 01. Searching and Sorting › 5. Selection and Order Statistics ›

Quickselect

Quickselect Quickselect finds the k-th smallest element in an unsorted array. It uses the same partition idea as Quicksort but only recurses into one side, which reduces work. You use it when you need a single order statistic such as median, top-k, or percentile, without fully sorting the array. Problem Given an array $A$ of length $n$ and an integer $k$ with $0 \le k < n$, find a value...
algorithms selection quickselect order-statistics
Wiki › Algorithms › 01. Searching and Sorting › 5. Selection and Order Statistics ›

Top K by Quickselect

Top K by Quickselect Top K by Quickselect finds the $k$ largest elements by partitioning the array so that the top $k$ elements occupy one side. It uses the same idea as Quickselect, but returns a set instead of a single element. This method is faster than heap-based approaches when the data is in memory and only a single pass with partitioning is needed. Problem Given an array $A$ of...
algorithms selection top-k quickselect