Valid Parentheses

Given a string s containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid. An input string is valid if:
1 Open brackets must be closed by the same type of brackets.
2 Open brackets must be closed in the correct order.
3 Every close bracket has a corresponding open bracket of the same type.
Example 1:
Input: s = "()" Output: true
Example 2:
Input: s = "()[]{}" Output: true