comefrom: <qiyuangong>268_Missing_Number_1.java
code: public int missingNumber(int[] nums) {
          int res = nums.length;
          for (int i = 0; i < nums.length; i++) {
              res ^= i;
              res ^= nums[i];
          }
          return res;
      }
masked: public int sample_funcname ( int [ ] var_0 ) {
    int var_2 = var_0 . length ;
    for ( int var_4 = 0 ;
    var_4 < var_0 . length ;
    var_4 ++ ) {
      var_2 ^= var_4 ;
      var_2 ^= var_0 [ var_4 ] ;
    }
    return var_2 ;
  }
  