Question 3.
This is your interview question.
Question 3. Longest Valid Parentheses
Given a string containing just the characters '(' and ')', return the length of the longest valid (well-formed) parentheses substring.
Example 1:
Input: s = "(()"
Output: 2
Explanation: The longest valid parentheses substring is "()".
Example 2:
Input: s = ")()())"
Output: 4
Explanation: The longest valid parentheses substring is "()()".
Example 3:
Input: s = ""
Output: 0
Constraints:
0 <= s.length <= 3 * 104s[i]is'(', or')'.
class Solution(object):
def longestValidParentheses(self, s):
"""
:type s: str
:rtype: int
"""