hdu1042 N!

题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=1042

N!

Time Limit: 10000/5000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 58278    Accepted Submission(s): 16547

Problem Description

Given an integer N(0 ≤ N ≤ 10000), your task is to calculate N!

 

Input

One N in one line, process to the end of file.

 

Output

For each N, output N! in one line.

 

Sample Input

1

2

3

 

Sample Output

1

2

6

 

题目大意：求N!        比如求123!我们肯定是要1*2*3*.....*123；如果直接这样做下去，毋庸置疑的会超时，那么我们就要将他一位一位存下来。一位一位的乘过去。做过的东西，还要想好久，还是不扎实，一定要多动脑。

 

详见代码。

#include <iostream>
#include <cstdio>
#include <cstring>

using namespace std;
int num[80000];
int main ()
{
    int n,pre;
    while (~scanf("%d",&n))
    {
        memset(num,0,sizeof(num));
        num[0]=1;
        int len=1;
        for (int i=2; i<=n; i++)
        {
            pre=0;
            for (int j=0; j<len; j++)
            {
                num[j]=num[j]*i+pre/10;
                pre=num[j];
                num[j]=num[j]%10;
            }
            while (pre>9)
            {
                num[len]=pre/10%10;
                len++;
                pre/=10;
            }
        }
        for (int i=len-1; i>=0; i--)
            printf ("%d",num[i]);
        printf ("
");
    }
    return 0;
}