# 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 ...

correct order (last-opened, first-closed — the LIFO property). 1. Build a mapping from each closing bracket to its expected opening partner. 2. Iterate over every character in the string. - If it is ...