C++ only, ~10 min

You are given a string s consisting only of the characters '(', ')', '{', '}', '[' and ']'. Determine whether the input string is valid according to these rules:

1. Every opening bracket must be closed by the same type of bracket.
2. Opening brackets must be closed in the correct order (the most recently opened unmatched bracket must be closed first).
3. Every closing bracket must have a corresponding opening bracket of the same type.

Return true if the string is valid, and false otherwise.

Example 1:

Input: s = "()"

Output: true

Example 2:

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

Output: true

Example 3:

Input: s = "(]"

Output: false

Constraints:

• 1 <= s.length <= 1000
• s consists of parentheses only: '()[]{}'.