From a21a06567385b416f94ddb95d612aee4d8410049 Mon Sep 17 00:00:00 2001
From: shrut_512 <84448891+Shrut012@users.noreply.github.com>
Date: Mon, 31 Oct 2022 21:57:31 +0530
Subject: [PATCH] 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 | 32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)
 create mode 100644 Longest Valid Parentheses.cpp

diff --git a/Longest Valid Parentheses.cpp b/Longest Valid Parentheses.cpp
new file mode 100644
index 0000000..8a50df8
--- /dev/null
+++ b/Longest Valid Parentheses.cpp	
@@ -0,0 +1,32 @@
+/*
+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;
+    }
+};