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#include "leetcode.h"
class Solution {
public:
int longestValidParentheses(string s) {
int n = s.size(), ans = 0;
stack<int> stk;
for (int i = 0; i < n; i++) {
if (s[i] == '(')
stk.push(i);
else {
if (!stk.empty()) {
if (s[stk.top()] == '(')
stk.pop();
else
stk.push(i);
} else
stk.push(i);
}
}
if (stk.empty())
ans = n;
else {
int a = n, b = 0;
while (!stk.empty()) {
b = stk.top();
stk.pop();
ans = max(ans, a - b - 1);
a = b;
}
ans = max(ans, a);
}
return ans;
}
};
int main() {
Solution obj;
string s = ")()())";
cout << obj.longestValidParentheses(s);
}
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