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

Example 2:

Input: s = "()[]{}" Output: true

Example 3:

Input: s = "(]" Output: false

  Constraints:

1 <= s.length <= 10⁴
s consists of parentheses only '()[]{}'.