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_1 = var_0 . length ;
    for ( int var_2 = 0 ;
    var_2 < var_0 . length ;
    var_2 ++ ) {
      var_1 ^= var_2 ;
      var_1 ^= var_0 [ var_2 ] ;
    }
    return var_1 ;
  }
  