刷题总结——跳蚤（poj1091容斥+分解质因数）

#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<cmath>
#include<ctime>
#include<cctype>
#include<cstring>
#include<string>
#include<algorithm>
#include<vector>
#define ul unsigned long long
using namespace std;
vector<int>zhiyinzi;
ul ans=0,n,m;
inline ul ksm(ul a,ul b)
{
  ul temp=1;
  while(b)
  {
    if(b%2==1)  temp=temp*a;
    b=b/2;
    a=a*a;
  }
  return temp;
}
inline void dfs(int u,int tot,int f)
{
  if(u==zhiyinzi.size())    
  {
    ul temp=m/tot;
    ans+=f*ksm(temp,n);
    return;
  }
  dfs(u+1,tot*zhiyinzi[u],-f);
  dfs(u+1,tot,f);
}
int main()
{
  //freopen("a.in","r",stdin);
  cin>>n>>m;  
  ul temp=m;
  for(int i=2;i*i<=temp;i++)
  {
    if(temp%i==0)
    {
      zhiyinzi.push_back(i);  
      while(temp%i==0)  temp/=i;
    }
  }
  if(temp!=1)  zhiyinzi.push_back(temp);
  dfs(0,1,1);
  cout<<ans<<endl;
  return 0; 
}