Difference Between Element Sum and Digit Sum of an Array

Problem Description

You are given a positive integer array nums.

1. The element sum is the sum of all the elements in nums.
2. The digit sum is the sum of all the digits (not necessarily distinct) that appear in nums.

Return the absolute difference between the element sum and digit sum of nums.

Note that the absolute difference between two integers x and y is defined as |x - y|.

Examples

Example 1:

Input: nums = [1,15,6,3]
Output: 9
Explanation: 
The element sum of nums is 1 + 15 + 6 + 3 = 25.
The digit sum of nums is 1 + 1 + 5 + 6 + 3 = 16.
The absolute difference between the element sum and digit sum is |25 - 16| = 9.

Example 2:

Input: nums = [1,2,3,4]
Output: 0
Explanation:
The element sum of nums is 1 + 2 + 3 + 4 = 10.
The digit sum of nums is 1 + 2 + 3 + 4 = 10.
The absolute difference between the element sum and digit sum is |10 - 10| = 0.

Constraints

• 1 <= nums.length <= 2000
• 1 <= nums[i] <= 2000

Approach

To solve this problem, we follow these steps:

1. Initialization: Initialize two variables, element_sum and digit_sum, to zero.
2. Element Sum Calculation: Iterate through the array and add each integer to element_sum.
3. Digit Sum Calculation: For each integer in the array, repeatedly extract its last digit using the modulo operation, add this digit to digit_sum, and remove the last digit by performing integer division by 10.
4. Compute Absolute Difference: After processing all integers, compute the absolute difference between element_sum and digit_sum using Math.abs() and return the result.

Python3

class Solution:
    def differenceOfSum(self, nums: List[int]) -> int:
        element_sum = sum(nums)
        digit_sum = sum(int(digit) for num in nums for digit in str(num))
        return abs(element_sum - digit_sum)

Java

class Solution {
    public int differenceOfSum(int[] nums) {
        int element_sum = 0;
        int digit_sum = 0;
        for(int i=0;i<nums.length;i++){
            element_sum+=nums[i];

            int val = nums[i];
            int x;
            
            while(val>0){
                x = val%10;
                digit_sum +=x;
                val = val/10;
            }
        }
        return Math.abs(element_sum - digit_sum);
    }
}

C++

class Solution {
public:
    int differenceOfSum(vector<int>& nums) {
        int element_sum = 0;
        int digit_sum = 0;
        for (int i = 0; i < nums.size(); i++) {
            element_sum += nums[i];

            int val = nums[i];
            int x;
            
            while (val > 0) {
                x = val % 10;
                digit_sum += x;
                val = val / 10;
            }
        }
        return abs(element_sum - digit_sum);
    }
};