comefrom: <gouthampradhan>backtracking_GenerateParentheses_1.java
code: private void backTrack(List<String> list, String str, int open, int close, int n) {
      if (str.length() == n * 2) {
        list.add(str);
      } else {
        if (open < n) backTrack(list, str.concat("("), open + 1, close, n);
        if (close
            < open) 
        backTrack(list, str.concat(")"), open, close + 1, n);
      }
    }
masked: private void sample_funcname ( List < String > list , String str , int open , int close , int n ) {
    if ( str . length ( ) == n * 2 ) {
      list . add ( str ) ;
    }
    else {
      if ( open < n ) backTrack ( list , str . concat ( "(" ) , open + 1 , close , n ) ;
      if ( close < open ) backTrack ( list , str . concat ( ")" ) , open , close + 1 , n ) ;
    }
  }
  