Poj Solution 1604

http://poj.org/problem?id=1604

//* @author: 82638882@163.com
import java.util.Scanner;
public class Main
{
 public static void main(String[] args)
 {
  Scanner in=new Scanner(System.in);
  int[] b2=new int[]{6,2,4,8};
  int[] b3=new int[]{1,3,9,7};
  int[] b7=new int[]{1,7,9,3};
  int[] b9=new int[]{1,9,1,9};
  while(in.hasNext())
  {
   int n=in.nextInt();
   int e,a2=0,a3=0,a5=0,a7=0,a9=0;
   e=n;while((e=e/2)!=0) a2+=e;
   e=n;while((e=e/5)!=0) a5+=e;
   a3=f(n,3);
   a7=f(n,7);
   a9=f(n,9);
   int ans=1;
   a2-=a5;
   if(a2!=0){
        a2=a2%4;
        ans*=b2[a2];
    }
    ans*=b3[a3%4];
    ans=ans%10;
    ans*=b7[a7%4];
    ans=ans%10;
    ans*=b9[a9%4];
    ans=ans%10;
    System.out.printf("%5d",n);
    System.out.println(" -> "+ans);
   }
}

    public static int f(int n,int a)
    {
        if(n==0) return 0;
        else return f(n/2,a)+g(n,a);
    }
    public static int g(int n,int a)
    {
        if(n==0) return 0;
        else if(n%10< a) return n/10+g(n/5,a);
        else return n/10+1+g(n/5,a);
    }
}