Add 32_Longest_Valid_Parentheses.java

Author: Sean Prashad

Dynamic Programming/32_Longest_Valid_Parentheses.java

@@ -0,0 +1,28 @@
+class Solution {
+    public int longestValidParentheses(String s) {
+        if (s == null || s.length() == 0) {
+            return 0;
+        }
+
+        int[] dp = new int[s.length()];
+        dp[0] = 0;
+        int leftBracketCount = 0, result = 0;
+
+        for (int i = 0; i < s.length(); i++) {
+            if (s.charAt(i) == '(') {
+                ++leftBracketCount;
+            } else if (leftBracketCount > 0) {
+                dp[i] = dp[i - 1] + 2;
+
+                if (i - dp[i] > 0) {
+                    dp[i] += dp[i - dp[i]];
+                }
+
+                --leftBracketCount;
+                result = Math.max(result, dp[i]);
+            }
+        }
+
+        return result;
+    }
+}