Fear Factoring Gym - 101615C（除法分块）

http://codeforces.com/gym/101615/attachments

 1 #include <stdio.h>
 2 #include <string.h>
 3 
 4 unsigned long long solve(unsigned long long n)
 5 {
 6     unsigned long long l, r, re;
 7     re = 0;
 8     for(l=1;l<=n;l=r+1)
 9     {
10         r = n/(n/l);
11         re = re + (n/l)*(l+r)*(r-l+1)/2;
12     }
13     return re;
14 }
15 
16 int main()
17 {
18     unsigned long long a, b;
19     scanf("%lld %lld", &a, &b);
20     printf("%lld\n", solve(b) - solve(a-1));
21     return 0;
22 }

除了除法分块，还需要注意的是一定要用 unsigned 否则会wa。