Day 48: LeetCode 20 [Valid Parentheses]
Problem Description: 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 brackets. Open brackets must be closed in the correct order. Every close bracket has a corresponding open bracket of the same type.
Example 1: Input: s = "()" Output: true
Link to LeetCode Problem: https://leetcode.com/problems/valid-parentheses/description/
