2 5
2^? mod 2 = 1 2^4 mod 5 = 1
#include<iostream>
using namespace std;
int main()
{
int n,i,j;
while(cin>>n)
{
int ls[10000];int sum=1;
memset(ls,0,sizeof(ls));
for(i=1; ;i++)
{
sum*=2;
sum%=n;
if(sum==1)
{
cout<<"2^"<<i<<" mod "<<n<<" = 1"<<endl;
break;
}
if(ls[sum])
{
cout<<"2^? mod "<<n<<" = "<<"1"<<endl;
break;
}
ls[sum]=1;
}
}
return 0;
}
原文：http://blog.csdn.net/lsgqjh/article/details/44876899