大数阶乘

大数阶乘传送门

//大数阶乘
#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;

int a[50000];
int n;

int main(){
    scanf("%d",&n);
    memset(a,0,sizeof(a)); 
    int len = 1;
    a[1] = 1;
    int i,j;
    for( i = 1; i <= n; i++ ){
        for( j = 1; j <= len; j++ )
            a[j] *= i;
        for( j = 1; j <= len; j++ ){
            if( a[j] < 10 )
                continue ;
            int pos = j;
            while( pos<=len ){
                if( a[len] > 9 )
                    len++;
                a[pos+1] += a[pos]/10;
                a[pos] %= 10;
                pos++;
            }
        }
    }
    for( i = len; i >= 1; i-- )
        printf("%d",a[i]);
    printf("\n");
    return 0;
}