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Longest_Valid_Parenthesis.cpp
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Longest_Valid_Parenthesis.cpp
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class Solution {
public:
int longestValidParentheses(string s) {
stack<int> Stack;
int result = 0;
Stack.push(-1);
for(int i = 0; i < (int)s.length(); i++) {
if(s[i] == '(') {
Stack.push(i);
} else {
if(Stack.size() == 1 or s[Stack.top()] != '(') {
Stack.push(i);
} else {
Stack.pop();
result = max(result, i - Stack.top());
}
}
}
return result;
}
};
// Another way (slightly different)
class Solution {
public:
int longestValidParentheses(string s) {
stack <int> Stack;
int maxLen = 0;
int lastPos = -1;
for(int i = 0; i < s.length(); ++i) {
if(s[i] == '(') {
Stack.push(i);
} else {
if(Stack.empty()) {
lastPos = i;
} else {
Stack.pop();
if(Stack.empty()) {
maxLen = max(maxLen, i - lastPos);
} else {
maxLen = max(maxLen, i - Stack.top());
}
}
}
}
return maxLen;
}
};