factorial.cpp

用来计算N！最后一位非0数字

#include<iostream.h>
char c[20] = {6,6,2,6,4,2,2,4,2,8,4,4,8,4,6,8,8,6,8,2};

int factorial(int x)
{
    int m = 1;
    if(x <= 1)return 1;
    while(x > 0)
    {
      m *= c[x%20];
      m %= 10;
      x /= 5;  
    }
    return m;
}

int main()
{
    int x;
    cout<<"Please input your N  (0<N<20000000)  "<<endl;
    cin>>x;
    int y =factorial(x);
    cout<<"your N's factorial is:"<<y<<endl;
    system("pause");
    return 0;
}