poj2154(Polya+欧拉函数优化模版）

#include <cstdio>
#include <cstring>
#include<iostream>
using namespace std;
const int maxx=45000;
int p;
int vis[maxx];
bool primes[maxx];
int k=0;
void prime(){//素数筛
    int i,j;
    memset(primes,true,sizeof(primes));
    for(i=2;i<maxx;i++){
        if(primes[i]){
            vis[k++]=i;
            for(j=2*i;j<maxx;j+=i){
                primes[j]=false;
            }
        }
    }
}
 
int Euler_1(int n){//欧拉函数
    int res=n;
    for(int i=0;vis[i]*vis[i]<=n;i++){
        if(n%vis[i]==0){
            res=res/vis[i]*(vis[i]-1);
            while(n%vis[i]==0)  n/=vis[i];
        }
    }
    if(n>1)
      res=res/n*(n-1);
    return res%p;
}
 
int pows(int a,int b){//快速幂
    int ans=1;
    a%=p;
    while(b){
        if(b&1){
            ans=(ans*a)%p;
        }
        b>>=1;
        a=(a*a)%p;
    }
    return ans;
}
int main(){
    int i,t,n,tot;
    prime();
    cin>>t;
    while(t--){
        tot=0;
        cin>>n>>p;
        for(int i=1;i*i<=n;i++){    
			if(i*i==n){
				tot=tot+pows(n,i-1)*Euler_1(i)%p;
			}else if(n%i==0){
				tot=(tot+pows(n,i-1)*Euler_1(n/i)+pows(n,n/i-1)*Euler_1(i))%p;
			}
    	}
        cout<<tot%p<<endl;
    }
    return 0;
}

标签：vis,poj2154,模版,ans,tot,int,res,Polya,primes
来源： https://blog.csdn.net/Keep_Trying_Go/article/details/113842479