32. Longest Valid Parentheses
Given a string containing just the characters ‘(‘ and ‘)’, find the length of the longest valid (well-formed) parentheses substring.
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| class Solution {
public:
int longestValidParentheses(string s) {
vector<int> st {-1};
int res = 0;
for(int i = 0; i < s.length(); i++) {
if(s[i] == '(') {
st.push_back(i);
} else {
st.pop_back();
if(st.empty()) st.push_back(i);
else res = max(res, i - st.back());
}
}
return res;
}
};
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