poj1286 Necklace of Beads【裸polya】

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很裸的polya，不過我看polya看了很久

吉大ACM模板裡面也有

#include <cstdio>#include <cmath>#include <iostream>using namespace std;long long gcd(long long a,long long b){return b==0?a:gcd(b,a%b);}int main(){    #ifndef ONLINE_JUDGE//freopen("G:/1.txt","r",stdin);//freopen("G:/2.txt","w",stdout);#endiflong long p[33];p[0]=1;for(long long i=1;i<=24;i++){p[i]=p[i-1]*3;//cout<<p[i]<<endl;}long long res=0;long long s;while(cin>>s){        if(s==-1)            break;        if(s==0)        {            cout<<"0\n";            continue;        }long long res=s&1?s*p[s/2+1]:(s/2)*(p[s/2]+p[s/2+1]);for(long long k=1;k<=s;k++){res+=p[gcd(k,s)];}res/=2*s;cout<<res<<'\n';}    return 0;}