How does a C-language applet determine the difference between two dates?

Enter two dates and calculate the number of days for the difference. Two methods are used for implementation. The second method uses struct, and the code is clearer. The rest are the same.

1. Common writing

Copy codeThe Code is as follows:
# Include <stdio. h>
Int leapyear (int year)
{
If (year % 4 = 0 & amp; year % 100! = 0) | year % 400 = 0)
Return 1;
Else
Return 0;
}
Int days (int * day1, int * day2)
{
Int I = 0;
Int * tmp;
Int diff = 0;
Const int month [13] = {, 31, 31, 31 };
If (day1 [0] = day2 [0])
{
If (day1 [1] = day2 [1])
{
Diff = day1 [2]-day2 [2];
Diff = (diff <0 )? (-Diff): diff;
}
Else
{
If (day1 [1] <day2 [1]) // day1 = 1991-5-8 day2 = 1991-6-2
{
Tmp = day1; // day1 = 1991-6-2 day2 = 1991-5-8
Day1 = day2;
Day2 = tmp;
}
For (I = day2 [1] + 1; I <day1 [1]; I ++)
{
Diff + = month [I];
}
Diff + = month [day2 [1]-day2 [2] + day1 [2];
If (day2 [1] <= 2 & day1 [1]> 2)
If (leapyear (day2 [0])
Diff ++;
}
}
Else
{
If (day1 [0] <day2 [0])
{
Tmp = day1;
Day1 = day2;
Day2 = tmp;
}
For (I = day2 [0] + 1; I <day1 [0]; I ++)
{
If (leapyear (I ))
Diff ++ = 366;
Else
Diff ++ = 365;
}
For (I = day2 [1] + 1; I <= 12; I ++) // day1 = 1992-1-1 day2 = 1991-1-1
{
Diff + = month [I];
}
Diff + = (month [day2 [1]-day2 [2]);
If (day2 [1] <= 2)
If (leapyear (day2 [0])
Diff ++;
For (I = 1; I <day1 [1]; I ++)
{
Diff + = month [I];
}
Diff + = day1 [2];
If (day1 [1]> 2)
If (leapyear (day1 [0])
Diff ++;
}
Return diff;
}
Int main ()
{
Int day1 [3], day2 [3];
Int day = 0;
Printf ("input date :");
Scanf ("% d-% d", & day1 [0], & day1 [1], & day1 [2]);
Printf ("enter another date :");
Scanf ("% d-% d", & day2 [0], & day2 [1], & day2 [2]);
Day = days (day1, day2 );
Printf ("two dates have a total of % d days. N ", day );
Return 0;
}

2. Use struct to make the code more clean

Copy codeThe Code is as follows:
# Include <stdio. h>
Typedef struct date
{
Int year;
Int month;
Int day;
} DATE;
Int leapyear (int year)
{
If (year % 4 = 0 & amp; year % 100! = 0) | year % 400 = 0)
Return 1;
Else
Return 0;
}
Int compare (DATE * d1, DATE * d2) // if the first DATE is greater than the second one, exchange the DATE
{
DATE * tmp;
If (d1-> year = d2-> year) // The number of years is equal.
{
If (d1-> month> d2-> month) // The number of months is equal.
{
Tmp = d1;
D1 = d2;
D2 = d1;
}
Else if (d1-> month = d2-> month) // Date is equal
{
If (d1-> day> d2-> day)
{
Tmp = d1;
D1 = d2;
D2 = d1;
}
}
}
Else if (d1-> year> d2-> year)
{
Tmp = d1;
D1 = d2;
D2 = tmp;
}
Return 0;
}
Int diff (DATE * date1, DATE * date2)
{
Int I;
Int diff = 0;
Const int month [13] = {, 31, 31, 31 };
If (date1-> year = date2-> year)
{
If (date1-> month = date2-> month)
{
Diff = date2-> day-date1-> day;
}
Else
{
For (I = date1-> month + 1; I <date2-> month; I ++)
{
Diff + = month [I];
}
Diff + = month [date1-> month]-date1-> day + date2-> day;
If (leapyear (date1-> year ))
If (date1-> month <= 2 & date2-> month> 2)
Diff ++;
}
}
Else
{
For (I = date1-> year + 1; I <date2-> year; I ++)
{
If (leapyear (I ))
Diff ++ = 366;
Else
Diff ++ = 365;
}
For (I = date1-> month + 1; I <= 12; I ++) // how many days is date1 from the end of the year?
{
Diff + = month [I];
}
Diff + = month [date1-> month]-date1-> day;
If (date1-> month <= 2)
If (leapyear (date1-> year ))
Diff ++;
For (I = 1; I <date2-> month; I ++) // how many days is date2 from the beginning of the year?
{
Diff + = month [I];
}
Diff + = date2-> day;
If (date1-> month> 2)
If (leapyear (date2-> year ))
Diff ++;
}
Return diff;
}
Int main ()
{
Int days = 0;
DATE day1, day2;
DATE * date1, * date2;
Date1 = & day1;
Date2 = & day2;
Printf ("input date :");
Scanf ("% d-% d", & (date1-> year), & (date1-> month), & (date1-> day ));
Printf ("enter another date :");
Scanf ("% d-% d", & date2-> year, & date2-> month, & date2-> day );
Compare (date1, date2 );
Days = diff (date1, date2 );
Printf ("two dates have a total of % d days. N ", days );
Return 0;
}