hdu 1215 筛法

求小于n的n的因子之和

Sample Input

3
2
10
20
Sample Output

1

8

22

 1 #include<cstdio>
 2 #include<iostream>
 3 #include<algorithm>
 4 #include<cstring>
 5 #include<cmath>
 6 #include<queue>
 7 using namespace std;
 8 int n,m,t;
 9 const int maxint=500000;
10 int f[maxint+1];
11 void init()
12 {
13     int i,j;
14     f[1]=1;
15     for(i=1;i<=maxint/2;i++)        //因数
16     {
17         for(j=i*2;j<=maxint;j+=i)
18         {
19             f[j]+=i;
20         }
21     }
22 }
23 int main()
24 {
25     int i,j,k;
26     init();
27     //freopen("1.in","r",stdin);
28     scanf("%d",&t);
29     while(t--)
30     {
31         scanf("%d",&n);
32         printf("%d\n",f[n]);
33     }
34 }

 

转载于:https://www.cnblogs.com/cnblogs321114287/p/4277969.html