Merge pull request #684 from karan112005/karan112005-patch-1

Added Solution for LeetCode Problem No. 32

Author: Sirajmolla

LeetCode/32. Longest Valid Parentheses/Solution.java

@@ -0,0 +1,23 @@
+// https://leetcode.com/problems/longest-valid-parentheses/
+
+class Solution {
+    public int longestValidParentheses(String s) {
+        Stack<Integer> stack = new Stack();
+        stack.push(-1);
+        int maxLen = 0;
+        for(int i = 0; i < s.length(); i++)
+        {
+            if(s.charAt(i) == '(')
+                stack.push(i);
+            else if(s.charAt(i) == ')')
+            {    
+                stack.pop();
+                if(stack.empty())
+                    stack.push(i);
+                else
+                    maxLen = Math.max(maxLen, i - stack.peek());     
+            }
+        }
+        return maxLen;
+    }
+}