N！Again

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 4781    Accepted Submission(s): 2527

4 
5

24
120

看到n的范围  脑子里就知道是规律。。。

其实把结果输出一下就看到了。如果某个值正好整除2009  那么 后面的都是0了

import java.math.BigInteger;
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner sca=new Scanner(System.in);
		while(sca.hasNext()){
			int x=sca.nextInt();
			if(x>41){
				System.out.println(0);
				continue;
			}
			BigInteger res=BigInteger.ONE;
			for(int i=2;i<=x;i++){
				res=res.multiply(BigInteger.valueOf(i));
				res=res.mod(BigInteger.valueOf(2009));
			}
			System.out.println(res);
		}
	}

}

hdu2647 N！Again

原文：http://blog.csdn.net/su20145104009/article/details/52153883