uva10820 send a table (nlogn求1-n欧拉函数值模版

 1 #include<cstdio>
 2 #include<iostream>
 3 #include<cmath>
 4 #include<algorithm>
 5 #include<cstring>
 6 #include<cstdlib>
 7 #include<queue>
 8 #include<vector>
 9 #include<map>
10 #include<stack>
11 #include<string>
12 
13 using namespace std;
14 
15 int n;
16 int phi[50001];
17 int f[50001];
18 
19 int main(){
20     memset(phi,0,sizeof(phi));
21     memset(f,0,sizeof(f));
22     phi[1]=1;
23     for (int i=2;i<=50000;i++){
24             if (phi[i]==0){
25                     for (int j=i;j<=50000;j+=i){
26                             if (phi[j]==0) phi[j]=j;
27                             phi[j]=phi[j]/i*(i-1);
28                     }
29             }
30     }
31     for (int i=1;i<=50000;i++) f[i]=f[i-1]+phi[i];
32     while (scanf("%d",&n)==1){
33             if (n==0) return 0;
34             printf("%d\n",f[n]*2-1);
35     }
36     return 0;
37 }
38 /*
39 2
40 5
41 0
42 */