32-longest-valid-parentheses

32. Longest Valid Parentheses

Hard

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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 ')'.