关于Date类的运算问题

Question

不知道为什么间隔日期有的时候算不对，像1987 3 4 和1998 2 8 就不对，是哪里错了吗

/*
实现日期的下一天

两个日期  相减

日期+ 天数 得到的日期

具体要求：实现类date,其中

构造函数包括year,month,day三个参数

重载两个date类之间的-，以及date类的+=,-=

使用int year(),int month(),int day()返回三个参数*/
#include <iostream>
using namespace std;

class date
{
private:
    int y;
    int m;
    int d;
public:
    date(){};
    date(int yy,int mm,int dd);
    date(const date &t):y(t.y),m(t.m),d(t.d){};
    ~date(){};
    
    //输出 year,month,day
    int year()const{return y;}
    int month()const{return m;}
    int day()const{return d;}
    
    //判断是否闰年
    bool leapyear(int y) const;
    
    //得到某个月天数 
    int daysOfMonth(int y,int m)const;
    
    //改变日期
    date changeDays(const int days)const;  
    
    //重载运算符
    date& operator++();    //前置++ 
    date operator++(int); //后置++      
    
    //日期加上days天数
    friend date operator+(const date &t, const int days);
    friend date operator+(const int days, const date &t);
    date& operator +=(int days);
    
    //日期减去days天数
    friend date operator- (const date &t, const int days);
    friend int operator-(const date &t1, const date &t2);
    date& operator -=(int days); 
    
    //重载<,==
    friend bool operator<(const date &t1,const date &t2);
    friend bool operator ==(const date &d1,const date &d2); 
    
    //计算间隔天数
    int distance(const date &d)const; 
    
};

//构造函数 
date::date(int yy, int mm, int dd):y(yy),m(mm),d(dd)
{
    if(yy<=0 || mm<=0 || mm>12 || dd<=0||dd>daysOfMonth(y,m))
    {
        cout<<"Error invalid date: ";
        cout<<endl;
        exit(-1);
    }
}

//闰年 
bool date::leapyear(int yy) const
{
    return (yy%4 == 0 && yy % 100 != 0 || yy % 400 == 0);
}

//每个月天数
int date::daysOfMonth(int yy, int mm)const
{
    int days = 0;
    
    switch(mm)
    {
    case 1:
    case 3:
    case 5:
    case 7:
    case 8:
    case 10:
    case 12:
        days = 31;
        break;
    case 4:
    case 6:
    case 9:
    case 11:
        days = 30;
        break;
    case 2:
        days = 28+leapyear(yy);
        break;
    }
 
    return days;    
 } 
//改变日期
date date::changeDays(const int days)const
{
    int yearTemp = y;
    int monthTemp = m;
    int dayTemp = d;
 
    if(days>0){
        dayTemp += days;
 
        while(dayTemp>daysOfMonth(yearTemp,monthTemp)){
            dayTemp -= daysOfMonth(yearTemp,monthTemp);
 
            monthTemp++;
            if(monthTemp>12){
                yearTemp++;
                monthTemp = 1;
            }
        }
    }else{   //days为负数
        dayTemp += days;
 
        while(dayTemp<1){
            monthTemp--;
            if(monthTemp<1){
                yearTemp--;
                monthTemp = 12;
            }
            dayTemp += daysOfMonth(yearTemp,monthTemp);
        }
    }
 
    return date(yearTemp,monthTemp,dayTemp);
}

//前置
date & date::operator++()
{
    *this = this->changeDays(1);
    return *this;
}
 
date date::operator++(int)   //后置++
{
    date dTemp(*this);
    ++(*this);
    return dTemp;
} 

//日期加上days个天数
date operator +(const date &t,const int days)
{
    if(days==0){   //如果天数为0，返回当个月
        return t;
    }
    else
        return t.changeDays(days);
}
 
//日期加上days个天数的重载
date operator +(const int days,const date &t)
{
    if(days==0){   //如果天数为0，返回当个月
        return t;
    }
    else
        return t.changeDays(days);
}
 
//日期自身加上days个天数
date& date::operator +=(int days)
{
    if(days==0)
        return *this;
    else{
        *this = this->changeDays(days);
        return *this;
    }
}

//日期减去days个天数
date operator -(const date &t,const int days)
{
    if(days==0){   //如果天数为0，返回当个月
        return t;
    }
    else
        return t.changeDays(-days);
}
 
//两个日期相减，前一个日期必须大于后一个日期
int operator -(const date &t1,const date &t2)
{
    if(t1<t2){
        cout<<"被减数日期必须大于减数日期！"<<endl;
        exit(-1);
    }
    else if(t1==t2)
        return 0;
    else
        return t1.distance(t2);
}
 
//日期自身减去days个天数
date& date::operator -=(int days)
{
    if(days==0)
        return *this;
    else{
        *this = this->changeDays(-days);
        return *this;
    }
}

//重载小于号<
bool operator <(const date &t1,const date &t2)
{
    return t1.distance(t2)<0 ? true:false;
} 

//重载==
bool operator ==(const date &d1,const date &d2)
{
    return d1.distance(d2)==0 ? true:false;
} 

//计算间隔天数
int date::distance(const date &t) const
{
    //非闰年中当月前几个月的总天数 
    const int DAYS_OF_MONTH[] =
    {0,31,59,90,120,151,181,212,243,273,304,334,365};
 
    int years = y-t.y;
    int months = DAYS_OF_MONTH[m] - DAYS_OF_MONTH[t.m];
    int days = d-t.d;
 
    //4年一闰，100的倍数免润，400的倍数再闰
    int totalDays = years*365+years/4-years/100+years/400+months+days;
    return totalDays; 
 } 

//StudybarCommentBegin
int main(void) {
    using std::cin;
    using std::cout;
    using std::endl;
    date D1,D2;
    int year;
    int month;
    int day;
    cin>>year>>month>>day; //输入第一个日期 
    D1=date(year,month,day);
    cin>>year>>month>>day;  //输入第二个日期 
    D2=date(year,month,day);
    cout<<D2-D1<<endl; 
    cin>>day;  //输入要减去的天数 
    D1+=day;
    D2-=day;
    cout<<D1.year()<<" "<<D1.month()<<" "<<D1.day()<<endl;
    cout<<D2.year()<<" "<<D2.month()<<" "<<D2.day()<<endl;
    return 0;
}

//StudybarCommentEnd

Answer 1

distance函数写的不对，要修改一下：

int date::distance(const date &t) const
{
    //非闰年中当月前几个月的总天数 
    const int DAYS_OF_MONTH[] =
    { 0,31,59,90,120,151,181,212,243,273,304,334,365 };

    int years = y - t.y;
    int months = DAYS_OF_MONTH[m-1] - DAYS_OF_MONTH[t.m-1];//当月未完，应是到前一个月为止的总天数相减
    int days = d - t.d;

    //4年一闰，100的倍数免闰，400的倍数再闰
    int numLeapYear = 0;//不能根据年份差判断是否是闰年，需要逐年判断并结合具体月份
    for (int yy = t.y; yy <= y; yy++)
    {
        if ((yy == t.y && t.m > 2) || (yy == y && m < 3)) continue;
        numLeapYear += leapyear(yy) == true ? 1 : 0;
    }
    int totalDays = years * 365 + numLeapYear + months + days;
    return totalDays;
}