leetcode

0 // Brute force

1 class Solution {

2 public:

3 int differenceOfSums(int n, int m) const {

4 int res = 0;

5

6 for (int i = 1; i <= n; i++) {

7 if (i % m)

8 res += i;

9 else

10 res -= i;

11 }

12

13 return res;

14 }

15 };

16

17 // Math

18 class Solution {

19 public:

20 int differenceOfSums(int n, int m) const { return n * (n + 1) / 2 - m * (n / m) * (n / m + 1); }

21 };