大数阶乘

代码：

#include<iostream>
#include<algorithm>
#include<string.h>
using namespace std;
char a[102]={0},b[102][10000];
int k=2;
void js(int x)
{
	int cx=0,cb=0,i,j,t[3],s[10000]={0};
	cb=strlen(b[k]);
	if (x/10==0)
	{
		t[0]=x;
		cx=1;
	}
	else if (x/100==0)
	{
		t[0]=x/10;
		t[1]=x%10;
		cx=2;
	}
	else
	{
		t[0]=x/100;
		t[1]=x/10%10;
		t[2]=x%10;
		cx=3;
	}
	for (i=0;i<cb;i++)
	for (j=0;j<cx;j++)
	{
		s[i+j+1]+=(b[k][i]-'0')*t[j];
	}
	for (i=cb+cx-1;i>=0;i--)
	{
		if (s[i]>=10)
		{
			s[i-1]+=s[i]/10;
			s[i]%=10; 
		}
	}
	i=0;
	while (s[i]==0)
	{
		i++;
	}
	
	k++;
	for (j=0;i<cx+cb;i++,j++)
	{
		b[k][j]=s[i]+'0'; 
	}
	b[k][j]='\0';
}
int main()
{
	int n,i;
	strcpy(b[2],"2");
	for(i=3;i<101;i++)
	{
		js(i);
	}
	while (cin>>n)
	{
		if (n==0)
		 cout<<1<<endl;
		else if (n==1||n==2)
		 cout<<n<<endl;
		else
		{
			cout<<b[n]<<endl;
		}
	}
 }