Given a string s containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid. An input string is valid if: Open brackets must be closed by the same type of ...

It can be written as AB (A concatenated with B), where A and B are valid parentheses strings. It can be written as (A), where A is a valid parentheses string. You are given a parentheses string s and ...