Given a string, find the first non-repeating character in it and return it’s index. If it doesn’t exist, return -1. ExamplesNo.1s = “leetcode”return 0 ...

There are a total of n courses you have to take, labeled from 0 to n-1. Some courses may have prerequisites, for example to take course 0 you have to ...

There are a total of n courses you have to take, labeled from 0 to n-1. Some courses may have prerequisites, for example to take course 0 you have to ...

Given an array of n integers, and a moving window(size k), move the window at each iteration from the start of the array, find the sum of the element ...

A rectangle is represented as a list [x1, y1, x2, y2], where (x1, y1) are the coordinates of its bottom-left corner, and (x2, y2) are the coordinates ...

Given an array nums of n integers, find two integers in nums such that the sum is closest to a given number, target. Return the absolute value of diff ...

There are two properties in the node student id and scores, to ensure that each student will have at least 5 points, find the average of 5 highest sco ...

Given a string which consists of lowercase or uppercase letters, find the length of the longest palindromes that can be built with those letters. This ...

Given some points and an origin point in two-dimensional space, find k points which are nearest to the origin. Return these points sorted by distance, ...

Given a binary tree, find the subtree with maximum sum. Return the root of the subtree. NoteIt’s guaranteed that there is only one subtree with maximu ...