comefrom: <awangdev>560. Subarray Sum Equals K_2.java
code: private int[] calcPreSum(int[] nums) {
  
          int[] preSum = new int[nums.length + 1];
          for (int i = 1; i <= nums.length; i++) {
              preSum[i] += preSum[i - 1] + nums[i - 1];
          }
          return preSum;
      }
masked: private int [ ] sample_funcname ( int [ ] var_0 ) {
    int [ ] var_3 = new int [ var_0 . length + 1 ] ;
    for ( int var_4 = 1 ;
    var_4 <= var_0 . length ;
    var_4 ++ ) {
      var_3 [ var_4 ] += var_3 [ var_4 - 1 ] + var_0 [ var_4 - 1 ] ;
    }
    return var_3 ;
  }
  