add longest valid parentheses

leetcode/0032_longest_valid_parentheses.js

@@ -0,0 +1,56 @@
+function longestValidParentheses(string) {
+  let result = 0;
+  let dp = [];
+
+  for(let i = 0; i < string.length; i++) {
+    const letter = string[i];
+    dp[i] = 0;
+    if(letter === ")") {
+      if (string[i - 1] === "(") {
+        dp[i] = 2;
+
+        if (dp[i - 2] && dp[i - 2] > 0) {
+          dp[i] = dp[i] + dp[i - 2];
+        }
+        result = Math.max(dp[i], result);
+      }
+
+      if (string[i - 1] === ")") {
+        const index = i - dp[i - 1] - 1;
+        const isWrappingParentheses = string[index] === "(";
+
+        if (isWrappingParentheses) {
+          dp[i] = 2 + dp[i - 1];
+          if (dp[index - 1] > 0) {
+            dp[i] += dp[index - 1];
+          }
+        }
+
+        result = Math.max(dp[i], result)
+      }
+    }
+  }
+
+  return result;
+}
+
+let input = "()";
+console.assert(longestValidParentheses(input) === 2, 'first');
+
+input = "()()";
+console.assert(longestValidParentheses(input) === 4, 'second')
+
+input = "(())";
+console.assert(longestValidParentheses(input) === 4, 'third')
+
+input = "(()())";
+console.assert(longestValidParentheses(input) === 6, 'fourth')
+
+input = "))(())";
+console.assert(longestValidParentheses(input) === 4, 'fifth');
+
+input = ")()())";
+console.assert(longestValidParentheses(input) === 4, 'sixth')
+
+input = "()(())"
+console.assert(longestValidParentheses(input) === 6, 'seventh')