Add 921_Minimum_Add_to_Make_Parentheses_Valid.java

Author: Sean Prashad

Strings/921_Minimum_Add_to_Make_Parentheses_Valid.java

@@ -0,0 +1,22 @@
+class Solution {
+    public int minAddToMakeValid(String S) {
+        if (S == null || S.length() == 0) {
+            return 0;
+        }
+
+        int result = 0;
+        Stack<Character> s = new Stack<>();
+
+        for (char c : S.toCharArray()) {
+            if (c == '(') {
+                s.push(c);
+            } else if (s.isEmpty()) {
+                ++result;
+            } else {
+                s.pop();
+            }
+        }
+
+        return result + s.size();
+    }
+}