2894. Divisible and Non-divisible Sums Difference

You are given positive integers n and m.

Define two integers, num1 and num2, as follows:

• num1: The sum of all integers in the range [1, n] that are not divisible by m.
• num2: The sum of all integers in the range [1, n] that are divisible by m.

Return the integer num1 - num2.

class Solution {
public:
    int differenceOfSums(int n, int m) {
        int num1 = 0, num2 = 0;
        for(int i = 1; i <= n; i++) {
            if(i % m == 0) num2 += i;
            else num1 += i;
        }
        return num1 - num2;
    }
};