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Practice › LeetCode › LeetCode (archived) › LeetCode 09xx ›

LeetCode 949: Largest Time for Given Digits

Problem Restatement We are given an array arr containing exactly four digits. We need to use each digit exactly once to form a valid 24-hour time in this format: HH:MM The hour must be between: 00 and 23 The minute must be between: 00 and 59 Return the latest valid time that can be made. If no valid time can be made, return an empty string. The official statement defines...
leetcode array string permutation brute-force May 12, 2026
Practice › LeetCode › LeetCode (archived) › LeetCode 09xx ›

LeetCode 903: Valid Permutations for DI Sequence

Problem Restatement We are given a string s of length n . Each character is either: Character Meaning "I" Increasing "D" Decreasing We need to count how many permutations of the integers from 0 to n satisfy the pattern. A permutation has n + 1 numbers. For every index i : If s[i] == "I" , then perm[i] < perm[i + 1] . If s[i] == "D" , then perm[i]...
leetcode dynamic-programming prefix-sum permutation May 11, 2026
Practice › LeetCode › LeetCode (archived) › LeetCode 05xx ›

LeetCode 556: Next Greater Element III

Problem Restatement We are given a positive integer n . We need to rearrange its digits to form the smallest integer that is greater than n . The new integer must use exactly the same digits as n . If no greater integer can be formed, return -1 . If the answer is greater than the 32-bit signed integer limit, return -1 . The official constraint is: 1 <= n...
leetcode math string two-pointers permutation May 11, 2026
Practice › LeetCode › LeetCode (archived) › LeetCode 02xx ›

LeetCode 267: Palindrome Permutation II

Problem Restatement We are given a string s . Return all palindromic permutations of s without duplicates. A palindrome reads the same forward and backward. If no palindromic permutation exists, return an empty list. The answer may be returned in any order. The constraints are 1 <= s.length <= 16 , and s contains only lowercase English letters. Input and Output Item Meaning Input A lowercase string s Output List...
leetcode backtracking string hash-table permutation May 10, 2026
Practice › LeetCode › LeetCode (archived) › LeetCode 00xx ›

LeetCode 60: Permutation Sequence

Problem Restatement We are given two integers, n and k . The set is: [1, 2, 3, ..., n] This set has n! unique permutations. If we list all permutations in sorted order, we need to return the k th permutation as a string. The official constraints are 1 <= n <= 9 and 1 <= k <= n! . Input and Output Item Meaning Input Two integers n and...
leetcode math recursion permutation May 10, 2026