Given a string containing just the characters ( and ), return the length of its longest valid (well-formed) parentheses substring.
Examples
Example 1
- Input
- s = "(()"
- Output
- 2
- Why
- The longest valid run is ().
Example 2
- Input
- s = ")()())"
- Output
- 4
- Why
- The longest valid run is ()().
Example 3
- Input
- s = ""
- Output
- 0
Constraints
0 <= s.length <= 3 * 10^4- Each character is
(or).