C++练习 | 计算两日期之间天数差

#include<iostream>
#include<string>
#include<cstring>
using namespace std;

class Date
{
private:
    int year;
    int month;
    int day;
public:
    void get()
    {
        int a,b,c;
        cin>>a;
        getchar();
        cin>>b;
        getchar();
        cin>>c;
        year=a;
        month=b;
        day=c;
        return;
    }
    friend int days(Date a,Date b);
};

int days(Date a,Date b)
{
    int day1=0;
    Date temp;
    if((a.year<b.year)||((a.year==b.year)&&(a.month<b.month))||((a.year==b.year)&&(a.month==b.month)&&(a.day<b.day)))
    {
        temp=a;
        a=b;
        b=temp;//保证a比b日期靠后
    }
    if(a.year!=b.year)
    {
        day1+=(a.year-b.year-1)*365;//不考虑闰年和不完整年的整年天数
        day1+=((((a.year-1)/4) - ((a.year-1)/100) + ((a.year-1)/400))-(((b.year-1)/4) - ((b.year-1)/100) + ((b.year-1)/400)));//期间闰年天数
    for(int i=b.month;i<=12;i++)
    {
        switch(i)
        {
            case 1:
            {
                day1+=31;
                break;
            }
            case 2:
            {
                day1+=28;
                break;
            }
            case 3:
            {
                day1+=31;
                break;
            }
            case 4:
            {
                day1+=30;
                break;
            }
            case 5:
            {
                day1+=31;
                break;
            }
            case 6:
            {
                day1+=30;
                break;
            }
            case 7:
            {
                day1+=31;
                break;
            }
            case 8:
            {
                day1+=31;
                break;
            }
            case 9:
            {
                day1+=30;
                break;
            }
            case 10:
            {
                day1+=31;
                break;
            }
            case 11:
            {
                day1+=30;
                break;
            }
            case 12:
            {
                day1+=31;
                break;
            }
        }
    }
    day1-=b.day;
    for(int i=a.month-1;i>=1;i--)
    {
        switch(i)
        {
            case 1:
            {
                day1+=31;
                break;
            }
            case 2:
            {
                day1+=28;
                break;
            }
            case 3:
            {
                day1+=31;
                break;
            }
            case 4:
            {
                day1+=30;
                break;
            }
            case 5:
            {
                day1+=31;
                break;
            }
            case 6:
            {
                day1+=30;
                break;
            }
            case 7:
            {
                day1+=31;
                break;
            }
            case 8:
            {
                day1+=31;
                break;
            }
            case 9:
            {
                day1+=30;
                break;
            }
            case 10:
            {
                day1+=31;
                break;
            }
            case 11:
            {
                day1+=30;
                break;
            }
            case 12:
            {
                day1+=31;
                break;
            }
        }
    }
    day1+=a.day;
    if(((b.year%4==0&&b.year%100!=0)||(b.year%400==0))&&(b.month>2))
        day1-=1;
    if(((a.year%4==0&&a.year%100!=0)||(a.year%400==0))&&(a.month>2))
        day1+=1;
    }
    else
    {
        for(int i=b.month;i<a.month;i++)
        {
            switch(i)
            {
                case 1:
                {
                    day1+=31;
                    break;
                }
                case 2:
                {
                    day1+=28;
                    break;
                }
                case 3:
                {
                    day1+=31;
                    break;
                }
                case 4:
                {
                    day1+=30;
                    break;
                }
                case 5:
                {
                    day1+=31;
                    break;
                }
                case 6:
                {
                    day1+=30;
                    break;
                }
                case 7:
                {
                    day1+=31;
                    break;
                }
                case 8:
                {
                    day1+=31;
                    break;
                }
                case 9:
                {
                    day1+=30;
                    break;
                }
                case 10:
                {
                    day1+=31;
                    break;
                }
                case 11:
                {
                    day1+=30;
                    break;
                }
                case 12:
                {
                    day1+=31;
                    break;
                }
            }
        }
        day1+=a.day;
        day1-=b.day;
        if(b.month==2&&b.day==29)
            day1++;
        if(((a.year%4==0&&a.year%100!=0)||(a.year%400==0))&&(b.month<=2&&b.day!=29&&a.month>2))
        {
            day1++;
        }
    }
    return day1;
}

int main()
{
    Date y1,y2;
    y1.get();
    y2.get();
    cout<<days(y1,y2);
    return 0;
}