Easy way to determine leap year in ruby?

Question

Is there an easy way to determine if a year is a leap year?

Answer 1

def leap_year?(num)
 if num%4 == 0 && num%100 != 0  
    true
 elsif num%400 == 0 
    true
 elsif num%4 == 0 && num%100 == 0 && num%400 != 0 
    false
  elsif num%4 != 0 
    false
  end
end 
puts leap_year?(2000)

Answer 2

The variable n takes year to test and prints true if it's a leap year and false if it's not.

n=gets.to_i 
n%4==0 ? n%100==0 ? n%400 ?(puts true):(puts false) :(puts true) :(puts false)

Answer 3

This one takes a range:

(starting..ending).each do |year|
  next if year % 4   != 0
  next if year % 100 == 0 && year % 400 != 0
  puts year
end

Source: Learn to Program by Chris Pine

Answer 4

Using the least amount possible of comparisons, you could do this:

• First/Longer version

def leap_year?(year)
  # check first if year is divisible by 400
  return true if year % 400 == 0
  year % 4 == 0 && year % 100 != 0
end

• Shorter version

We can do the same check using short circuit OR (||):

def leap_year?(year)
  year % 400 == 0 || (year % 4 == 0 && year % 100 != 0)
end

Answer 5

Try this:

is_leap_year = year % 4 == 0 && year % 100 != 0 || year % 400 == 0

Answer 6

Use Date#leap?.

now = DateTime.now 
flag = Date.leap?( now.year ) 

e.g.

Date.leap?( 2018 ) # => false

Date.leap?( 2016 ) # => true