USACO Section 3.2 Factorials - 高精度模拟~

应改有更科学的方法吧~~我就是纯高精度了~~稍微估计了一下~~只做到1000位~~每次加进来都吧后缀0去掉~~最终输出第一位就ok了~~

Program:

/*  
ID: zzyzzy12  
LANG: C++  
TASK: fact4
*/    
#include<iostream>    
#include<istream>
#include<stdio.h>    
#include<string.h>    
#include<math.h>    
#include<stack>
#include<algorithm>    
#include<queue> 
#define oo 2000000000
#define ll long long
using namespace std;
int a[1005],n;
void mul(int k)
{
      int i,m;
      for (i=1;i<=1000;i++) a[i]*=k;
      i=1;
      for (i=1;i<1000;i++)
      {
            a[i+1]+=a[i]/10;
            a[i]%=10; 
      } 
      a[1000]%=10;
      for (m=1;m<1000;m++)
        if (a[m]!=0) break;
      m--;
      if (m)
      for (i=1;i<1000-m;i++) 
      {
             a[i]=a[i+m];
             a[i+m]=0;
      }
}
int main()
{
      freopen("fact4.in","r",stdin);  
      freopen("fact4.out","w",stdout);  
      memset(a,0,sizeof(a)); 
      a[1]=1; 
      scanf("%d",&n); 
      for (int i=1;i<=n;i++) 
        mul(i);
      printf("%d\n",a[1]); 
      return 0;   
}