# 閏年の判定
def leap_year?(year)
  return true if year % 400 == 0
  return false if year % 100 == 0
  return true if year % 4 == 0

  return false
end

puts leap_year?(2000)
# true
puts leap_year?(2011)
# false
puts leap_year?(2012)
# true
puts leap_year?(2100)
# false
puts leap_year?(2200)
# false
puts leap_year?(2300)
# false
puts leap_year?(2400)
# true