欧拉函数模板

 1 1 #include<iostream>
 2  2 #include<cstdlib>
 3  3 #include<cstdio>
 4  4 #include<cstring>
 5  5 #include<algorithm>
 6  6 #include<cmath>
 7  7 using namespace std;
 8  8 int phi[66000];
 9  9 int main()
10 10 {
11 11     int i , j ;
12 12     for ( i = 2 ; i <=  65536 ; i ++ )
13 13         phi[i]=0;
14 14     phi[1]=1;
15 15     for ( i = 2 ; i <=  65536 ; i ++ )
16 16         if ( !phi[i] )
17 17         {
18 18             for ( j = i ; j <=  65536 ; j += i )
19 19             {
20 20                 if ( !phi[j] )
21 21                     phi[j] = j ;
22 22                 phi[j] = phi[j] / i * (i - 1 ) ;
23 23             }
24 24         }
25 25 
26 26     int n ;
27 27     while ( cin >> n )
28 28         cout<<phi[n-1]<<endl;
29 29 
30 30     return 0;
31 31 }