Hust oj 2019 n! problem II(大数阶乘）

#include<iostream>
#include<cstring>

using namespace std;

int main()
{
int a[300];
int n;
while(cin>>n)
{
int i,j,k;
int sum,ans=0;
int num=1;
a[0]=1;
for(i=2;i<=n;i++)
{
for(j=1;j<=num;j++)
{
sum=a[j-1]*i+ans;
a[j-1]=sum%10;
ans=sum/10;
}
while(ans)
{
a[num++]=ans%10;
ans/=10;
}
}
for(i=num-1;i>=0;i--)
{
cout<<a[i];
}
cout<<endl;
}
}