计算N的阶乘

#include 
    
      using namespace std; int main() {
       int a[1024] = {
   0};     int n = 0;     while (scanf("%d",&n) == 1){
           memset(a, 0, sizeof(a));         a[0] = 1;//代表从1开始乘         int k = 1000;         for (int i = 2; i <= n; ++i){
               int c = 0;//进位             for (int j = 0; j < k; ++j){
                   int s = a[j] * i + c;                 a[j] = s % 10;                 c = s / 10;             }         }         while (k > 0 && a[k] == 0)             k--;         for (int i = k; i >= 0; --i)             printf("%d",a[i]);         printf("\n");     }     return 0; }