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.
Input: s = "()"
Output: true
Input: s = "()[]{}"
Output: true
Input: s = "(]"
Output: false
1 <= s.length <= 104
s consists of parentheses only '()[]{}'.