32. Longest Valid Parentheses

class Solution {
    public int longestValidParentheses(String s) {
        int n = s.length();
        int[] stack = new int[n + 1];
        int top = -1;
        int max = 0;
        stack[++top] = -1;
        for (int i = 0; i < n; i++) {
            if (s.charAt(i) == '(') {
                stack[++top] = i;
            } else {
                top--;
                if (top < 0) {
                    stack[++top] = i;
                } else {
                    max = Math.max(max, i - stack[top]);
                }
            }
        }
        return max;
    }
}

class Solution:
    def longestValidParentheses(self, s: str) -> int:
        n = len(s)
        stack = [-1]
        max_length = 0

        for i in range(n):
            if s[i] == '(':
                stack.append(i)
            else:
                stack.pop()

                if not stack:
                    stack.append(i)
                else:
                    max_length = max(max_length, i - stack[-1])

        return max_length

class Solution {
public:
    int longestValidParentheses(string s) {
        int n = s.length();
        vector<int> stack;
        stack.push_back(-1);

        int maxLength = 0;

        for (int i = 0; i < n; i++) {
            if (s[i] == '(') {
                stack.push_back(i);
            } else {
                stack.pop_back();

                if (stack.empty()) {
                    stack.push_back(i);
                } else {
                    maxLength = max(maxLength, i - stack.back());
                }
            }
        }

        return maxLength;
    }
};

var longestValidParentheses = function(s) {
    const stack = [-1];
    let maxLength = 0;

    for (let i = 0; i < s.length; i++) {
        if (s[i] === '(') {
            stack.push(i);
        } else {
            stack.pop();

            if (stack.length === 0) {
                stack.push(i);
            } else {
                maxLength = Math.max(maxLength, i - stack[stack.length - 1]);
            }
        }
    }

    return maxLength;
};