2894. Divisible and Non-divisible Sums Difference

Intuition

The problem requires us to find the difference between two sums:

1. Sum of numbers from 1 to n that are NOT divisible by m
2. Sum of numbers from 1 to n that are divisible by m

We can solve this by iterating through numbers 1 to n and checking if each number is divisible by m using the modulo operator.

Approach

1. Initialize two variables:
   • nd for sum of non-divisible numbers
   • d for sum of divisible numbers
2. Iterate through numbers from 1 to n
3. For each number i:
   • If i is divisible by m (i % m == 0), add it to d
   • If i is not divisible by m, add it to nd
4. Return the difference (nd - d)

Complexity

• Time complexity: O(n)
• Space complexity: O(1)

Keywords

• Math
• Modulo Operation

Code

func differenceOfSums(n int, m int) int {
    nd, d := 0, 0
    for i := 1; i <= n; i += 1 {
        if i % m == 0 {
            d += i
        } else {
            nd += i
        }
    }
    return nd - d
}