kaiguogit

def fizzbuzz(startnumber,endnumber)
  #check input for Fixnum
  if !(startnumber.is_a?(Fixnum) && endnumber.is_a?(Fixnum))
    puts "invalid input"
    return nil
  end

  #check start number is smaller than end number
  if startnumber > endnumber
    puts "Start number #{startnumber} is greater than end number #{endnumber}, reverting the loop"

kaiguogit

# Find the maximum 
def maximum(arr)
  arr.inject(arr[0]) do |sum,a| 
    a > sum ? a : sum
  end
end

# expect it to return 42 below
result = maximum([2, 42, 22, 02])
puts "max of 2, 42, 22, 02 is: #{result}"