Robina Li

Given an m x n matrix mat, return an array of all the elements of the matrix in a diagonal order.

Given an integer array nums, rotate the array to the right by k steps, where k is non-negative.

This page collects ready-to-use Java templates for every major binary search pattern you’ll encounter on LeetCode — from basic sorted-array lookup to rotated arrays, 2D matrices, and “search on the...

Given an integer array nums and two integers lower and upper, return the number of range sums that lie in [lower, upper] inclusive.

Given a binary tree, find the lowest common ancestor (LCA) of two given nodes in the tree.

Design a data structure that supports adding new words and finding if a string matches any previously added string.

There is a restaurant with a single chef. You are given an array customers, where customers[i] = [arrival_i, time_i]:

You have a set of integers s, which originally contains all the numbers from 1 to n. Unfortunately, due to some error, one of the numbers in s got duplicated...

Given a string s which consists of lowercase or uppercase letters, return the length of the longest palindrome that can be built with those letters.

Given a string s, find the first non-repeating character in it and return its index. If it does not exist, return -1.