Problem Given an array of strings strs, group the anagrams together. You can return the answer in any order. Definition Anagram Definition Examples For example, suppose that we have the following strings: Example 1: Input: strs = ["eat","tea","tan","ate","nat","bat"] Output: [ ["bat"],["nat","tan"],["ate","eat","tea"] ] ...
Problem Given n non-negative integers representing an elevation map where the width of each bar is 1, compute how much water it can trap after raining. Examples Example 1: ...
Problem Given a collection of candidate numbers (candidates) and a target number (target), find all unique combinations in candidates where the candidate numbers sum to target. Each number in candidates may only be used once in the combination. Note: The solution set must not contain duplicate combinations. Examples Example 1: Input: candidates = [10,1,2,7,6,1,5], target = 8 Output: [ [1,1,6], [1,2,5], [1,7], [2,6] ] ...
Problem Given an unsorted integer array, find the first missing positive integer. Follow up You have to find the smallest positive number missing from the array in O(n) time using constant extra space. You can modify the original array. Examples Example 1: Input: nums = [1,2,0] Output: 3 ...
Problem Given an array of distinct integers candidates and a target integer target, return a list of all unique combinations of candidates where the chosen numbers sum to target. You may return the combinations in any order. The same number may be chosen from candidates an unlimited number of times. Two combinations are unique if the frequency of at least one of the chosen numbers is different. It is guaranteed that the number of unique combinations that sum up to target is less than 150 combinations for the given input. ...
Problem Given an array of integers nums sorted in non-decreasing order, find the starting and ending position of a given target value. If target is not found in the array, return [-1, -1]. You must write an algorithm with O(log n) runtime complexity. Examples Example 1: Input: nums = [5,7,7,8,8,10], target = 8 Output: [3,4] ...
Problem Suppose a sorted array is rotated at some pivot unknown to you beforehand. (i.e., [0, 1, 2, 4, 5, 6, 7] might become [4, 5, 6, 7, 0, 1, 2]). You are given a target value to search. If found in the array return its index, otherwise return -1. You may assume no duplicate exists in the array. Follow up: what if duplicates are allowed? ...
Problem Given an integer array nums of length n and an integer target, find three integers in nums such that the sum is closest to target. Return the sum of the three integers. You may assume that each input would have exactly one solution. Examples Example 1: Input: nums = [-1,2,1,-4], target = 1 Output: 2 Explanation: The sum that is closest to the target is 2. (-1 + 2 + 1 = 2). ...
Problem You have n coins and you want to build a staircase with these coins. The staircase consists of k rows where the ith row has exactly i coins. The last row of the staircase may be incomplete. Given the integer n, return the number of complete rows of the staircase you will build. Examples Example 1: $$ \begin{matrix} \colorbox{orange} $ \\ \colorbox{orange} $ & \colorbox{orange} $ \\ \colorbox{orange} $ & \colorbox{orange} $ &\colorbox{white} 0 \end{matrix} $$ ...
Problem You are given two m x n binary matrices grid1 and grid2 containing only 0’s (representing water) and 1’s (representing land). An island is a group of 1’s connected 4-directionally (horizontal or vertical). Any cells outside of the grid are considered water cells. An island in grid2 is considered a sub-island if there is an island in grid1 that contains all the cells that make up this island in grid2. ...