Given a string containing just the characters '(' and ')', find 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 * 104 -
s[i]is'(', or')'.
SOLUTION:
class Solution:
def longestValidParentheses(self, s: str) -> int:
n = len(s)
stack = [-1]
mlen = 0
for i, c in enumerate(s):
if c == '(':
stack.append(i)
elif len(stack) > 0:
stack.pop()
if len(stack) > 0:
mlen = max(mlen, i - stack[-1])
else:
stack.append(i)
return mlen
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