switch on a tuple

Leap
Leap in C# 
public static class Leap
{
    public static bool IsLeapYear(int year)
    {
        return (year % 4, year % 100, year % 400) switch
        {
            (_, _, 0) => true,
            (_, 0, _) => false,
            (0, _, _) => true,
            _ => false,
        };
    }
}

A tuple is made from the conditions for the year being evenly divisible by 4, 100 and 400.

The tuple is tested in a switch expression. It checks the values of the expressions in the tuple, and uses the _ discard pattern to disregard a value. The default arm of the switch returns false when none of the previous arms match.

year year % 4 year % 100 year % 400 is leap year
2020 0 20 20 true
2019 3 19 19 false
2000 0 0 0 true
1900 0 0 300 false

Although some may consider it to be a more "functional" approach, the switch on a tuple approach is somewhat more verbose than other approaches, and may also be considered less readable.

4th Sep 2024 · Found it useful?

Other Approaches to Leap in C#

Other ways our community solved this exercise
public static bool IsLeapYear(int year)
{
    return year % 4 == 0 && (year % 100 != 0 || year % 400 == 0);
}
Boolean chain

Use a chain of boolean expressions. 

public static bool IsLeapYear(int year)
{
    return year % 100 == 0 ? year % 400 == 0 : year % 4 == 0;
}
Ternary operator

Use a ternary operator of boolean expressions. 

public static bool IsLeapYear(int year)
{
    return (new DateTime(year, 2, 28)).AddDays(1.0).Day == 29;
}
DateTime addition

Use DateTime addition. 

public static bool IsLeapYear(int year)
{
    return DateTime.IsLeapYear(year);
}
Built-in method

Use the built-in method.