Create Longest Valid Parentheses.cpp

Given a string containing just the characters '(' and ')', return the length of the longest valid (well-formed) parentheses substring.

Longest Valid Parentheses.cpp

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+/*
+Given a string containing just the characters '(' and ')', return the length of the longest valid (well-formed) parentheses substring.
+
+ 
+
+Example 1:
+
+Input: s = "(()"
+Output: 2
+Explanation: The longest valid parentheses substring is "()".
+*/
+
+class Solution {
+public:
+    int longestValidParentheses(string s) {
+        stack<int> stk;
+        stk.push(-1);
+        int maxL=0;
+        for(int i=0;i<s.size();i++)
+        {
+            int t=stk.top();
+            if(t!=-1&&s[i]==')'&&s[t]=='(')
+            {
+                stk.pop();
+                maxL=max(maxL,i-stk.top());
+            }
+            else
+                stk.push(i);
+        }
+        return maxL;
+    }
+};