Nyoj ___ Big Data factorial

Http://acm.nyist.net/JudgeOnline/problem.php? Pid = 28

Big Data factorial time limit: 3000 MS | memory limit: 65535 KB difficulty: 3

Description

We all know how to calculate a factorial of a number. But if this number is large, how should we calculate it and output it?

Input

Enter an integer m (0 <m <= 5000)

Output

Output the factorial of m, and enter a linefeed after the output ends.

Sample Input

50

Sample output

30414093201713378043612608166064768844377641568960512000000000000

Program code:

 1 #include<stdio.h> 2 #include<math.h> 3 int main(){ 4     int n; 5     while(scanf("%d",&n)!=EOF){ 6             long a[10000]; 7             int i,j,l,c,m=0,w; 8             a[0]=1; 9             for(i=1;i<=n;i++){10                 c=0;11                 for(j=0;j<=m;j++){12                     a[j]=a[j]*i+c;13                     c=a[j]/10000;14                     a[j]=a[j]%10000;15                 }16                 if(c>0) {m++;a[m]=c;}17             }18 19         w=m*4+log10(a[m])+1;20         printf("%ld",a[m]);21         for(i=m-1;i>=0;i--) printf("%4.4ld",a[i]);22         printf("\n");23     }24     return 0;25 }

The calculation method of the number of factorial digits is (int) log10 (x) + 1.
This is the number of digits of x.
Log10 (n !) = Log10 (1) + log10 (2) + log10 (3) +... + log10 (n)