Problem Statement The Recover Binary Search Tree LeetCode Solution – “Recover Binary Search Tree” states that given the root of the binary search tree, where the values of exactly two nodes are swapped by mistake. We need to recover the tree without changing its structure. Example: Input: root = [1,3,null,null,2] Output: [3,1,null,null,2] …
Problem Statement Closest Leaf in a Binary Tree LeetCode Solution – Given the root of a binary tree where every node has a unique value and a target integer k, return the value of the nearest leaf node to the target k in the tree. Nearest to a leaf means the least number of edges traveled on the binary tree to …
Problem Statement Ugly Number II LeetCode Solution – An ugly number is a positive integer whose prime factors are limited to 2, 3, and 5. Given an integer n, return the nth ugly number. Input: n = 10 Output: 12 Explanation: [1, 2, 3, 4, 5, 6, 8, 9, 10, 12] is the sequence of the first 10 …
Problem Statement Invalid Transactions LeetCode Solution – A transaction is possibly invalid if: the amount exceeds $1000, or; if it occurs within (and including) 60 minutes of another transaction with the same name in a different city. You are given an array of strings transaction where transactions[i] consists of comma-separated values representing the name, time (in minutes), amount, and city …
Problem Statement Find a Peak Element II LeetCode Solution – A peak element in a 2D grid is an element that is strictly greater than all of its adjacent neighbors to the left, right, top, and bottom. Given a 0-indexed m x n matrix mat where no two adjacent cells are equal, find any peak element mat[i][j] and return the length 2 array [i,j]. You may assume …
Problem Statement Combination Sum IV LeetCode Solution – Given an array of distinct integers nums and a target integer target, return the number of possible combinations that add up to target. The test cases are generated so that the answer can fit in a 32-bit integer. Input: nums = [1,2,3], target = 4 Output: 7 Explanation: The possible …
Problem Statement The String to Integer (atoi) Leetcode Solution -“String to Integer (atoi)” states that Implementing the myAtoi(string s) function, which converts a string to a 32-bit signed integer (similar to C/C++’s atoi function). The algorithm for myAtoi(string s) is as follows: Read in and ignore any leading whitespace. Check if the next character (if …
Problem Statement The Restore IP Addresses LeetCode Solution – “Restore IP Addresses” states that given the string which contains only digits, we need to return all possible valid IP Addresses in any order that can be formed by inserting dots into the string. Note that we’re not allowed to return …
Problem Statement String Compression LeetCode Solution – Given an array of characters chars, compress it using the following algorithm: Begin with an empty string s. For each group of consecutive repeating characters in chars: If the group’s length is 1, append the character to s. Otherwise, append the character followed by the group’s length. The compressed string …
Problem Statement Check Completeness of a Binary Tree LeetCode Solution – Given the root of a binary tree, determine if it is a complete binary tree. In a complete binary tree, every level, except possibly the last, is completely filled, and all nodes in the last level are as far left as possible. …