credit_chek.rb

#Valid: 5541808923795240, 4024007136512380, 6011797668867828
#Invalid: 5541801923795240, 4024007106512380, 6011797668868728


arr = []
arr1 = []
card_number = "6011797668867828"
card_number.split('')
arr << card_number[0]
arr << card_number[2]
arr << card_number[4]
arr << card_number[6]
arr << card_number[8]
arr << card_number[10]
arr << card_number[12]
arr << card_number[14]

arr1 << card_number[1]
arr1 << card_number[3]
arr1 << card_number[5]
arr1 << card_number[7]
arr1 << card_number[9]
arr1 << card_number[11]
arr1 << card_number[13]
arr1 << card_number[15]

arr1 = arr1.map do |num|
    num.to_i
    end

arr3 = arr.map do |num|
        num.to_i * 2
    end

arr4 = arr3.map do |num|
        if num > 9
            num - 9
        else
            num
        end
    end

arr5 = (arr1 << arr4).flatten

sum = arr5.inject(:+)

if test = sum % 10 == 0
then p "The number is valid!"
else p "The number is invalid"
end