determine wether a year is a leap year

jovani101 (8)
i have an assignment that asks me to input a year and then output if the yer is a leap year or not.

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#include <iostream>
using namespace std;

//prototypes
void intro();
int getYear(int);
bool leapYear(int);
bool showYear(int,bool);

int main()
{
    int date;
    bool leapyear;

    intro();
    date = getYear(date);
    leapyear = leapYear(date);
    showYear(date,leapyear);
    return 0;
}
void intro()
{
    cout << "\tThis will show you if a year is a leap year or not\n\n";
    return;
}
int getYear(int)
{
    int year;

    cout << "Enter a year: ";
    cin >> year;
    return year;
}
bool leapYear(int year)
{
    bool leap;
    int leap_year;
    int leap4;
    int leap100;
    int leap400;

    leap4 = year / 4;
    leap100 = year / 100;

    if (leap4 == year/4)
    {
        if (leap100 == year/100)
        {
            leap = true;
        }
        else
           leap = false;
    }
    return leap;
}
bool showYear (int year,bool leap)
{
    if (leap == true)
        cout << year << " is a leap year";
    else
        cout << year << " is not a leap year";
    return leap;
}

i was wondering if i am on the right track with all the if/else statements or if there is a simpler way?
Last edited on
dhayden (5798)
There's a simpler way.

Look at it this way:
If year / 4 has a remainder then its NOT a leap year.
Otherwise if year/100 has a remainder then it IS a leap year
otherwise if year/400 has a remainder then it is NOT a leap year
otherwise it is a leap year.

You can use the % operator for remainder. e.g. year % 4 gives the remainder after dividing year by 4 (assuming year is positive).
lastchance (6980)
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bool isLeap( int year )
{
   return !(year%4) - !(year%100) + !(year%400);
}
jovani101 (8)
what does the exclamation point mean?
lastchance (6980)
not
jovani101 (8)
i guess i am having trouble fully understanding what each thing means.

i get the NOT and the %operator but then why are you subtracting and adding?
Duthomhas (13208)
He’s using boolean expressions, which have a value of 0 or 1.

You should use some if statements, just like in dhayden’s answer.

For example, you can tell if a number is ODD or EVEN:

    If the number is evenly divisible by 2, then it is EVEN
    otherwise it is ODD

This translates very cleanly to a function:

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bool is_odd( int n )
{
  if ((n % 2) == 0) return false; // it is even if (n / 2) has a remainder of 0
  else return true; // it is odd
}

Making a function to determine whether a year is a leap year works on the very same principle:

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bool is_leap_year( int year )
{
  if (...)       // if (year / 4) has a non-zero remainder then NOT a leap year
  else if (...)  // if (year / 100) has a non-zero remainder then IS a leap year
  else if (...)  // if (year / 400) has a non-zero remainder then NOT a leap year
  else          // IS a leap year
}

Hope this helps.
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