comefrom: <awangdev>448. Find All Numbers Disappeared in an Array_1.java
code: private void swap(int[] nums, int a, int b) {
  
          int temp = nums[a];
          nums[a] = nums[b];
          nums[b] = temp;
      }
masked: private void var_0 ( int [ ] var_1 , int var_2 , int var_3 ) {
    int var_4 = var_1 [ var_2 ] ;
    var_1 [ var_2 ] = var_1 [ var_3 ] ;
    var_1 [ var_3 ] = var_4 ;
  }
  