Problem Given a linked list, swap every two adjacent nodes and return its head. You must solve the problem without modifying the values in the list’s nodes (i.e., only nodes themselves may be changed.) Examples Example 1: --- title: Input --- graph LR; 1 --> 2:::focus --> 3 -->4:::focus classDef focus fill:#f96 --- title: Output --- graph LR; 2:::focus --> 1 --> 4:::focus -->3 classDef focus fill:#f96 ...
Problem Determine if a 9 x 9 Sudoku board is valid. Only the filled cells need to be validated according to the following rules: Each row must contain the digits 1-9 without repetition. Each column must contain the digits 1-9 without repetition. Each of the nine 3 x 3 sub-boxes of the grid must contain the digits 1-9 without repetition. Note: A Sudoku board (partially filled) could be valid but is not necessarily solvable. Only the filled cells need to be validated according to the mentioned rules. The Sudoku board could be partially filled, where empty cells are filled with the character ‘.’. ...
Problem You are given an m x n binary matrix grid. An island is a group of 1’s (representing land) connected 4-directionally (horizontal or vertical.) You may assume all four edges of the grid are surrounded by water. The area of an island is the number of cells with a value 1 in the island. Return the maximum area of an island in grid. If there is no island, return 0. ...
Problem Given the root of a binary tree and an integer targetSum, return the number of paths where the sum of the values along the path equals targetSum. The path does not need to start or end at the root or a leaf, but it must go downwards (i.e., traveling only from parent nodes to child nodes). Examples Example 1: ...
Problem Given a sorted array arr[] of n elements, write a function to search a given element x in arr[]. Input: A sorted array, arrA[] and an key Output : Return index if element is found, else -1. Examples Example 1: Input: nums = [-1,0,3,5,9,12], target = 9 Output: 4 Explanation: 9 exists in nums and its index is 4 ...
Problem Given an array A of integers and integer K, return the maximum S such that there exists i < j with A[i] + A[j] = S and S < K. If no i, j exist satisfying this equation, return -1. Examples Example 1: Input: A = [34,23,1,24,75,33,54,8], K = 60 Output: 58 Explanation: We can use 34 and 24 to sum 58 which is less than 60. ...
Problem You are given a 0-indexed, strictly increasing integer array nums and a positive integer diff. A triplet (i, j, k) is an arithmetic triplet if the following conditions are met: i < j < k, nums[j] - nums[i] == diff, and nums[k] - nums[j] == diff. Return the number of unique arithmetic triplets. Examples Example 1: Input: nums = [0,1,4,6,7,10], diff = 3 Output: 2 Explanation: (1, 2, 4) is an arithmetic triplet because both 7 - 4 == 3 and 4 - 1 == 3. (2, 4, 5) is an arithmetic triplet because both 10 - 7 == 3 and 7 - 4 == 3. ...
Problem Given an integer array nums with possible duplicates, randomly output the index of a given target number. You can assume that the given target number must exist in the array. Implement the Solution class: Solution(int[] nums) Initializes the object with the array nums. int pick(int target) Picks a random index i from nums where nums[i] == target. If there are multiple valid i’s, then each index should have an equal probability of returning. Examples Example 1: ...
Problem There are two sorted arrays nums1 and nums2 of size n. Find the median of the two sorted arrays. You may assume nums1 and nums2 cannot be both empty. OR There are 2 sorted arrays A and B. Write an algorithm to find the median of the array obtained after merging the above 2 arrays(i.e. array of length 2n). The complexity should be O(log(n)) Median Definition Median Definition ...