You are given an integer array nums and you have to return a new countsarray. The counts array has the property where counts[...

Given a string which contains only lowercase letters, remove duplicate letters so that every letter appear once and only once...

Given a 2D board and a list of words from the dictionary, find all words in the board. Each word must be constructed from let...

Design a data structure that supports the following two operations: 12void addWord(word)bool search(word) search(word) can s...

Given a range [m, n] where 0 <= m <= n <= 2147483647, return the bitwise AND of all numbers in this range, inclusive...

Given a binary tree, imagine yourself standing on the right side of it, return the values of the nodes you can see ordered fr...

All DNA is composed of a series of nucleotides abbreviated as A, C, G, and T, for example: “ACGAATTCCG”. When studying DNA, i...

Given a string s1, we may represent it as a binary tree by partitioning it to two non-empty substrings recursively. Below is ...

Given a 2D binary matrix filled with 0’s and 1’s, find the largest rectangle containing only 1’s and return its area. Example...

Given a string s, you are allowed to convert it to a palindrome by adding characters in front of it. Find and return the shor...