POJ 1091 跳蚤

 1 #include <iostream>
 2 using namespace std;
 3 typedef long long LL;
 4 const int maxn = 50;
 5 LL p[maxn],n,m,ret,tot;
 6 LL quickPow(LL base,LL index){
 7     LL ret = 1;
 8     while(index){
 9         if(index&1) ret *= base;
10         index >>= 1;
11         base *= base;
12     }
13     return ret;
14 }
15 void init(LL x){
16     tot = 0;
17     for(int i = 2; i*i <= x; ++i){
18         if(x%i == 0){
19             p[tot++] = i;
20             while(x%i == 0) x /= i;
21         }
22     }
23     if(x > 1) p[tot++] = x;
24 }
25 int main(){
26     ios::sync_with_stdio(false);
27     while(cin>>n>>m){
28         init(m);
29         for(int i = 1; i < (1<<tot); ++i){
30             int cnt = 0;
31             LL tmp = 1;
32             for(int j = 0; j < tot; ++j){
33                 if((i>>j)&1){
34                     cnt++;
35                     tmp *= p[j];
36                 }
37             }
38             if(cnt&1) ret += quickPow(m/tmp,n);
39             else ret -= quickPow(m/tmp,n);
40         }
41         cout<<(quickPow(m,n) - ret)<<endl;
42     }
43     return 0;
44 }