C++判断日期为一年中第几天

[zjfgavin]

我刚学C++，遇到一道题目：输入年月日，输出该日期为这一年的第几天？涉及到闰年。自己写了代码，编译没问题，但输入日期后运行出错（dubge error),烦请高手帮忙，先谢谢了。
代码如下:
//===============================================================================================
//date.cpp
//===============================================================================================
#include <iostream>
using namespace std;
//-----------------------------------------------------------------------------------------------
int main ()
{
int year,month,day,a,b,i;
cout<<"Please input a date as 'yyyy mm dd'"<<"After input every pate please press 'Enter'"<<endl;
cin>>year>>month>>day;
//-------------------------------------------------
{
if((year%4==0)&&(year%100!=0)||(year%400==0))
a=1;
else
a=0;
}
//-------------------------------------------------
if (!((year>1980) && (month<13) && (day<32)))
cout<<"The date don't comform to routines"<<endl;
else
{
//-------------------------------------------
for(i=0;i<month;i++)
{
if (i=2)
b=b+28+a;
else
if (((i%2==1)&&(i<8))||((i%2==0)&&(i>7)))
b=b+31;
else
b=b+30;
}
//--------------------------------------------
cout<<"The day is the "<<b<<"of the year"<<endl;
}
}
//==============================================================================================

[leiXure]

是不是死循环了？
输入合法性检查之后：
if(i=2)
应该是
if(i == 2)

P.S. 在判断两个数是否相等的时候，最好将常量值放在 == 的左边，这样如果你把 == 误写成了 =，编译就会出错，不会等到运行时才被发现，所以上面那一句，更好的写法是
if(2 == i)

[zjfgavin]

谢谢

[michaelbupt2009]

楼主的程序健壮性稍微欠缺。
以下是一个参考程序。

#include <iostream>
using namespace std;
#include <stdio.h>
struct daynum
{
int year;
int month;
int day;
}data;
static bool temp;
static bool cheaktemp=1;
int leap[12]={31,29,31,30,31,30,31,31,30,31,30,31};
int calculate(daynum &,int[]);
bool leapyear(int &);
bool cheak();
void input();
void output(int);
void main()
{
do {input();temp=leapyear(data.year);}while (!cheak());
output(calculate(data,leap));
}
void input()
{
cout<<"请输入年、月、日："<<endl;
cin>>data.year>>data.month>>data.day;
}
void output(int number)
{
if(data.month<3)
cout<<"您输入的日期在该年的第 "<<number<<" 天"<<endl;
else
{
if(temp)
cout<<"您输入的日期在该年的第 "<<number<<" 天"<<endl;
else
cout<<"您输入的日期在该年的第 "<<number-1<<" 天"<<endl;
}
}
int calculate(daynum &ptdata,int *ptleap)
{
int sum=0;
if (ptdata.month==1)
return ptdata.day;
else
{
for (int i=0;i<(ptdata.month-1);i++)
{
sum+=ptleap[i];
}
return (sum+ptdata.day);
}
}
bool leapyear(int &year)
{
return (year%4==0&&year%100!=0)||(year%400==0);
}

bool cheak()
{
if(data.month>12||data.month<1)
{cheaktemp=0; goto jump;}
if(data.month==2)
{
if(temp)
{
if(data.day>29||data.day<1)
cheaktemp=0
}
else
{
if(data.day>28||data.day<1)
cheaktemp=0;
}
}
else if(data.month==1||data.month==3||data.month==5||data.month==7||data.month==8||data.month==10||data.month==12)
{
if(data.day>31||data.day<1)
cheaktemp=0;
}
else
{
if (data.day<1||data.day>30)
cheaktemp=0;
}
jump:
if(!cheaktemp) cout<<"时间数据有错误！"<<endl<<endl;
return cheaktemp;
}

[jenglev]

//=============================================================================================== 
//date.cpp 
//=============================================================================================== 
#include <iostream> 
using namespace std; 
//----------------------------------------------------------------------------------------------- 
int main () 
{ 
	int year,month,day,a,b=0,i; 
	cout <<"Please input a date as 'yyyy mm dd'\n" <<"After input every pate please press 'Enter'" <<endl; 
	cin>>year>>month>>day; 
//------------------------------------------------- 
	{ 
	if((year%4==0)&&(year%100!=0)||(year%400==0)) 
		a=1; 
	else 
		a=0; 
	} 
//------------------------------------------------- 
	if (!((year>1980) && (month <13) && (day <32)))
		cout <<"The date don't comform to routines" <<endl; 
	else
	{ 
	//------------------------------------------- 
		for(i=1;i <month;i++) //从1开始
		{ 
			if (i==2) 
			b=b+28+a; 
			else 
			if (((i%2==1)&&(i <8))||((i%2==0)&&(i>7))) 
			b=b+31; 
			else 
			b=b+30; 
		} 
		b+=day; //day没有加
		//-------------------------------------------- 
		cout <<"The day is the " <<b <<" of the year" <<endl; 

	} 
	system("pause");
} 
//==============================================================================================

帮你改好了，自己看看吧