给一组括号，remove最少的括号使得它valid

 package fb;

 public class removeParen {

     public static String fix(String str) {

         StringBuffer res = new StringBuffer(str);

         int l = 0, r = 0;

         int i = 0;

         while (i < res.length()) {

             if (res.charAt(i) == '(') l++;

             else {

                 if (l <= r) {

                     res.deleteCharAt(i);

                     i--;

                 }

                 else {

                     r++;

                 }

             }

             i++;

         }

         l = 0;

         r = 0;

         i = res.length()-1;

         while (i >= 0) {

             if (res.charAt(i) == ')') r++;

             else {

                 if (l >= r) {

                     res.deleteCharAt(i);

                 }

                 else {

                     l++;

                 }

             }

             i--;

         }

         return res.toString();

     }

     /**

      * @param args

      */

     public static void main(String[] args) {

         // TODO Auto-generated method stub

         String res = fix(")((())(");

         System.out.println(res);

     }

 }