Problem Statement: Flatten Binary Tree to Linked List LeetCode Solution: Given the root of a binary tree, flatten the tree into a “linked list”: The “linked list” should use the same TreeNode class where the right child pointer points to the next node in the list and the left child pointer is always null. The “linked list” should be …
Problem Statement Valid Triangle Number LeetCode Solution – Given an integer array nums, return the number of triplets chosen from the array that can make triangles if we take them as side lengths of a triangle. Input: nums = [2,2,3,4] Output: 3 Explanation: Valid combinations are: 2,3,4 (using the first 2) …
Unique Binary Search Trees LeetCode Solution says that – Given an integer n, return the number of structurally unique BST’s (binary search trees) which has exactly n nodes of unique values from 1 to n. Example 1: Input: n = 3 Output: 5 Example 2: Input: n = 1 Output: 1 Constraints: 1 <= n <= 19 …
Range Sum of BST LeetCode Solution says that – Given the root the node of a binary search tree and two integers low and high, return the sum of values of all nodes with a value in the inclusive range [low, high]. Example 1: Input: root = [10,5,15,3,7,null,18], low = 7, high = 15 Output: 32 Explanation: …
Problem Statement Reverse Integer LeetCode Solution says that – Given a signed 32-bit integer x, return x with its digits reversed. If reversing x causes the value to go outside the signed 32-bit integer range [-231, 231 – 1], then return 0. Assume the environment does not allow you to store 64-bit integers (signed or unsigned). Example 1: …
Problem Statement Find K Closest Elements LeetCode Solution – Given a sorted integer array arr, two integers k and x, return the k closest integers to x in the array. The result should also be sorted in ascending order. An integer a is closer to x than an integer b if: |a – x| < |b – x|, or |a – x| == |b – …
Problem Statement Continuous Subarray Sum LeetCode Solution – Given an integer array nums and an integer k, return true if nums has a continuous subarray of the size of at least two whose elements sum up to a multiple of k, or false otherwise. An integer x is a multiple of k if there exists an integer n such that x = n * k. 0 is always a …
Problem Statement Vertical Order Traversal of Binary Tree LeetCode Solution says – Given the root of a binary tree, calculate the vertical order traversal of the binary tree. For each node at position (row, col), its left and right children will be at positions (row + 1, col – 1) and (row + 1, col + 1) respectively. …
Problem Statement Top K Frequent Elements LeetCode Solution Says that – Given an integer array nums and an integer k, return the k most frequent elements. You may return the answer in any order. Example 1: Input: nums = [1,1,1,2,2,3], k = 2 Output: [1,2] Example 2: Input: nums = [1], k = 1 Output: [1] …
Problem Statement: Valid Triangle Number LeetCode Solution says – Given an integer array nums, return the number of triplets chosen from the array that can make triangles if we take them as side lengths of a triangle. Example 1: Input: nums = [2,2,3,4] Output: 3 Explanation: Valid combinations are: 2,3,4 (using …