倒计时完善2.cpp

一个自己编写简单的程序

#include <stdio.h>
#include <math.h>
#include <iostream.h>
void days(int m,int n);
void scan();
int daysofmonth(int m);
int year,month,day,overyear,overmonth,overday;
int cnt=0;

void main()
{
  	int i;
	scan();
	if  (month==overmonth)
		days(day,overday);	
	else if (month+1==overmonth)
	{
		days(day,daysofmonth(month));
		days(1,overday);
	}  
	else 
	{
		days(day,daysofmonth(month));
		for (i=month+1;i<=overmonth-1;i++)
			days(1,daysofmonth(i));
		days(1,overday);
	}  
	cout<<"从"<<month<<"月"<<day<<"日"<<"到"<<overmonth<<"月"<<overday<<"日还有"<<cnt-1<<"天";
	cin>>i;
}

void scan()
{ 
loop:   cout<<"\n";
		cout<<"请输入倒计时开始日期";
		/*cin>>year;*/
		cin>>month;
		if (month>12) 
		{cout<<"输入的月份是错误的，一年没有"<<month<<"月"; goto loop;}
		cin>>day;
		if (day>daysofmonth(month))
		{cout<<"输入的日期是错误的"<<month<<"月没有"<<day<<"号"; goto loop;}
		cout<<"请输入倒计时截止日期";
	 	/*cin>>overyear;*/
		cin>>overmonth;	
		if (overmonth>12) 
		{cout<<"输入的月份是错误的，一年没有"<<overmonth<<"月"; goto loop;}
		if (overmonth<month)
		{cout<<"输入的截止日期早于开始日期，怎么倒计时？"; goto loop;}
		cin>>overday;	
		if (overday>daysofmonth(overmonth))
		{cout<<"输入的日期是错误的"<<overmonth<<"月没有"<<overday<<"号"; goto loop;}
		if (overmonth==month && overday<day)
		{cout<<"输入的截止日期早于开始日期，怎么倒计时？"; goto loop;}  
}

void days(int m,int n)
{ 
  int i;
  for (i=m;i<=n;i++)
	  cnt++;
}
                
int daysofmonth(int m)
{
  switch (m)
  {
    case 1:
	case 3:
	case 5:
	case 7:
	case 8:
	case 10:
	case 12:return 31;
	case 4:
	case 6:
	case 9:
	case 11:return 30;
	case 2:if (((year%4==0 && year%100!=0)||year%400==0))
	          return 29;
           else 
			  return 28;
    default:  return 0;
  }
}