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Class definition
class Date {
public:
Date(int y = 1, int m = 1, int d = 1)
{
//判断日期是否有效
if (y <= 0 || m <= 0 || m > 12 || d <= 0 || d > getday(y, m))
{
//日期无效
y = 1;
m = 1;
d = 1;
cout << "日期无效,设为默认值：1-1-1" << endl;
}
else
{
_y = y;
_m = m;
_d = d;
}
}
private:
int _y;
int _m;
int _d;
};
First look at the definition of the class:
there are three data members in the class, _y, _m, and _d represent the year, month, and day respectively.
A constructor with default parameters is defined, and the date format judgment is also added to the constructor. If the date is invalid, the object will be initialized with the reference value (1-1-1).
getday（）
int getday(int y, int m)
{
static int days[] = {
0,31,28,31,30,31,30,31,31,30,31,30,31 };
int day = days[m];
//如果为二月，并且为闰年，修改天数
if (m == 2 && (((y % 4 == 0) && (y % 100 != 0)) || (y % 400 == 0)))
day += 1;
return day;
}
The function of this function is to get the number of days in the current month and create a static array to store the number of days. The first element of the array is set to 0. In this way, the index of the array can be regarded as a month, which is convenient for operation.
February is divided into 29 days in a leap month and 28 days in a flat month. Pay attention and judge.
Overloaded operator +=
//日期的运算
//Date += int
//左操作数改变为相加后的结果
//2021。2.4 + 90 ： 2021.2.94 -28 ---> 2021.3.66 - 31 ---> 2021.4.35 - 30 ---> 2021.5.5
Date& operator+=(int day)
{
//首先天数相加
_d += day;
//判断是否溢出
while (_d > getday(_y, _m))
{
//减去当月天数
_d -= getday(_y, _m);
//月份进位
++_m;
//月份是否溢出
if (_m == 13)
{
//年份进位
++_y;
//月份更新为一月
_m = 1;
}
}
//返回相加之后的结果
return *this;
}
Overloading the += operator is to add the object of the class to the number of days.
For example:
Date a（2021，1，1）+=1； //该操作后a对象的值应该变为a(2021,1,2)
Here, it should be noted that after the month overflows, the year is carried in 1, and the month is re-assigned to January
Friend function overloading<<
ostream& operator<<(ostream& _cout, const Date& d)
{
//_cout << d._y << "-" << d._m << "-" << d._d;
printf("%04d-",d._y);
printf("%02d-", d._m);
printf("%02d", d._d);
return _cout;
}
Here, the friend function overloading << operator
is used. Objects of the class can be directly output with the standard output stream object, which is more intuitive.
Complete code
Computer postgraduate retest questions: date accumulation
#define _CRT_SECURE_NO_WARNINGS 1
#include<iostream>
using namespace std;
class Date {
public:
friend ostream& operator<<(ostream& _cout, const Date& d);
Date(int y = 1, int m = 1, int d = 1)
{
//判断日期是否有效
if (y <= 0 || m <= 0 || m > 12 || d <= 0 || d > getday(y, m))
{
//日期无效
y = 1;
m = 1;
d = 1;
cout << "日期无效,设为默认值：1-1-1" << endl;
}
else
{
_y = y;
_m = m;
_d = d;
}
}
int getday(int y, int m)
{
static int days[] = {
0,31,28,31,30,31,30,31,31,30,31,30,31 };
int day = days[m];
//如果为二月，并且为闰年，修改天数
if (m == 2 && (((y % 4 == 0) && (y % 100 != 0)) || (y % 400 == 0)))
day += 1;
return day;
}
//日期的运算
//Date += int
//左操作数改变为相加后的结果
//2021。2.4 + 90 ： 2021.2.94 -28 ---> 2021.3.66 - 31 ---> 2021.4.35 - 30 ---> 2021.5.5
Date& operator+=(int day)
{
//首先天数相加
_d += day;
//判断是否溢出
while (_d > getday(_y, _m))
{
//减去当月天数
_d -= getday(_y, _m);
//月份进位
++_m;
//月份是否溢出
if (_m == 13)
{
//年份进位
++_y;
//月份更新为一月
_m = 1;
}
}
//返回相加之后的结果
return *this;
}
private:
int _y;
int _m;
int _d;
};
ostream& operator<<(ostream& _cout, const Date& d)
{
//_cout << d._y << "-" << d._m << "-" << d._d;
printf("%04d-",d._y);
printf("%02d-", d._m);
printf("%02d", d._d);
return _cout;
}
int main()
{
int i = 0;
cin >> i;
int y, m, d,num;
while (i-- > 0)
{
cin >> y >> m >> d >> num;
Date a(y, m, d);
a += num;
cout << a << endl;
}
return 0;
}