n!.cpp

输入一个自然数n

#include<iostream.h>
#include<string.h>
#include<stdlib.h> 
int n;
void count()
{
	int m,flag=0,top=1,zero=0,fac[10000]={0},add[10000]={0};
	fac[1]=1;
	int i,j;
	for(i=1;i<n+1;i++)
	{
		for(j=1;j<=top;j++)
		{
			fac[j]=fac[j]*i;
			if((fac[j])>9)
			{
				m=fac[j]%10;
				add[j]+=(fac[j]-m)/10;
				fac[j]=m;
				if(j==top)
					flag++;
			}
		}
		for(j=1;j<top+1;j++)
		{
			fac[j]+=add[j-1];
			add[j-1]=0;
			if(fac[j]>9)
			{
				m=fac[j]%10;
				add[j]+=(fac[j]-m)/10;
				fac[j]=m;
			}
		}
		for(;add[j-1]>9;j++)
		{
			fac[j]=add[j-1];
			add[j-1]=0;
			m=fac[j]%10;
			add[j]+=(fac[j]-m)/10;
			fac[j]=m;
			flag++;
		}
		if(add[j-1]>0)
		{
			fac[j]=add[j-1];
			add[j-1]=0;
		}
		if(flag)
			top+=flag;
            flag=0;
	}
	cout<<n<<"!=";
	for(i=top;i>0;i--)
	{
		cout<<fac[i];        /*******输出n!******/
		if(fac[i]==0)
			zero++;          /****计算0的个数****/
	}
	cout<<endl;
	cout<<"There are "<<zero<<" zeros!"<<endl;
}
/*******输入n*******/
void input()
{
	
	int flag;
	char t[100];
	do{
		flag=0;
		cout<<"type in n:";
		cin>>t;
		for(int i=0;i<strlen(t);i++)
		{
			if(t[i]<'0' ||t[i]>'9')
				flag=1;
		}
		if(flag)
			cout<<"input error! please try again!"<<endl;
	}while(flag);
	n=atoi(t);
}
/**********运行界面*********/
void  menu()
{
	cout<<"\t\t                  I------You               \n";
	cout<<"\t\t                    n!运算   \n";
	cout<<"\t\t    -------------------------------------\n"; 
	cout<<"\t\t                 1.输入阶数n\n";
	cout<<"\t\t                 0.退出\n";
	cout<<"\t\t    -------------------------------------\n";
	cout<<"\t\t                 B06020307丁飞  \n";
	cout<<"\t\t+-------------------------------------------+\n";
}
//接收菜单选择                             
char get_menu_choice()
{
char menu_choice[10];
 do
 {
	cout<<"---★--*Please Make Your choice*--★---\n＞＞＞";
	cin>>menu_choice;
  if(menu_choice[0]<'0' ||menu_choice[0]>'1'||strlen(menu_choice)>1)
  {	
	   if(strlen(menu_choice)>=9)
		{
   	   	    cout<<"输入有误,退出程序\n";
			exit(0);
		}
	  cout<<"input error, try again\n";
  }
 }while(menu_choice[0]<'0' || menu_choice[0]>'1'||strlen(menu_choice)>1);
 return menu_choice[0];
}
//菜单响应函数
void menu_done()
{
	while(1)
		{
		menu();
		switch(get_menu_choice())
			 {
				case '1': 
					input();          //输入n
					count();          //计算n!
					break;
				case '0':
					cout<<"\n谢谢使用再见!\n";
					exit(0);          //程序正常退出
				}
		}
}
//主函数
void main()
{
	menu_done();
}