HDOJ 2674-N！Again【数论】



N！Again

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 4266    Accepted Submission(s): 2278

Problem Description

WhereIsHeroFrom:             Zty, what are you doing ?
Zty:                                     I want to calculate N!......
WhereIsHeroFrom:             So easy! How big N is ?
Zty:                                    1 <=N <=1000000000000000000000000000000000000000000000…
WhereIsHeroFrom:             Oh! You must be crazy! Are you Fa Shao?
Zty:                                     No. I haven's finished my saying. I just said I want to calculate N! mod 2009


Hint : 0! = 1, N! = N*(N-1)!

 

Input

Each line will contain one integer N(0 <= N<=10^9). Process to end of file.

 

Output

For each case, output N! mod 2009

 

Sample Input

   
   
   
   

    
    
    
    4 
5
   
   
   
   

 

Sample Output

   
   
   
   

    
    
    
    24
120
   
   
   
   

 

Author

WhereIsHeroFrom

 

Source

HDU女生专场公开赛——谁说女子不如男

 

解题思路

根据阶乘的性质我们可以知道当阶乘数超过2009时，阶乘最后对2009取余时都等于0。另外注意for循环的结果都要对2009取余，否则有可能溢出。

#include<stdio.h>
int main()
{
	int a;
	while(scanf("%d",&a)!=EOF)
	{
		int s=1;
		if(a>2009)
		{
			printf("0\n");
		}
		else
		{
			for(int i=1;i<=a;i++)
			{
				s*=i;
				s=s%2009;
			}
			printf("%d\n",s);
		}
		
	}
	return 0;
}