A parentheses string is valid if and only if: It is the empty string, It can be written as AB (A concatenated with B), […]

You are given a 0-indexed string s of even length n. The string consists of exactly n / 2 opening brackets ‘[‘ and n / 2 closing brackets ‘]’. A string is called balanced if and only

You are given a string s consisting only of uppercase English letters. You can apply some operations to this string where, in one operation,

You are given two strings sentence1 and sentence2, each representing a sentence composed of words. A sentence is a list of words that are separated by a single space

Given two strings s1 and s2, return true if s2 contains a  permutation of s1, or false otherwise. In other words, return true if one of s1‘s permutations is the substring of s2. Example 1:

You are given a positive integer array skill of even length n where skill[i] denotes the skill of the ith player. Divide the players into n / 2 teams of size 2 such that