# Re: Checking Credit Cards (#122)

This is my first time submitting a solution to the quiz. I’ll attach my
.rb
file and copy / paste my solution below. It’s ugly, but it works.

Thanks,

Chase Southard

#!/usr/bin/env ruby

# Created by Chase Southard on 2007-05-01.

class CardValidator

def get_card_number
if \$*[0] == nil
puts “I need a card number. Please enter one now:”
cardnumber = \$stdin.gets.strip!
else
cardnumber = ARGV.shift
end
puts “You entered: #{cardnumber}”
@card_array = cardnumber.split(//).collect
#remove spaces
@card_array.compact!
end

def validate_card_prefix
#case statement to grab the first few digits
case @card_array.first.to_i
when 3
prefix = @card_array.slice(0, 2).join.to_i
#debug
#puts prefix
#puts prefix.class
if prefix == 34 || 37
if @card_array.length == 15
card_type = “AMEX”
puts “The card type entered was: #{card_type}”
else
“You might have bogus card.”
end
else
“You might have a bogus card.”
end
when 6
prefix = @card_array.slice(0,4).join.to_i
#debug
#puts prefix
#puts prefix.class
#puts “card length: #{@card_array.length}”
if prefix == 6011 && @card_array.length == 16
card_type = “Discover”
puts “The card type entered was: #{card_type}”
else
“You might have a bogus card.”
end
when 4
if @card_array.length == 13 || 16
card_type = “Visa”
puts “The card type entered was: #{card_type}”
else
“You might have a bogus card.”
end
when 5
prefix = @card_array.slice(0, 2).join.to_i
#puts prefix
#puts prefix.class
if prefix == 51 || 52 || 53 || 54
if @card_array.length == 16
card_type = “MasterCard”
puts “The card type entered was: #{card_type}”
else
“You might have a bogus card.”
end
end
end
end

def validate_luhn
array_size = @card_array.length

``````#starting at the LAST digit and working backwards gathering digits
``````

to
get the untouched elements of the card number

``````untouched_elements_index = Array.new
while array_size > 1
untouched_elements_index.push(array_size - 1)
array_size -= 2
end

untouched_elements = Array.new
untouched_elements_index.each { |e|
``````

untouched_elements.push(@card_array[e].to_i) }

``````#reset array size for the next part
array_size = @card_array.length

#Starting at the NEXT TO LAST digit and working backwards gathering
``````

digits to get the touched elements of the card number
every_other_element = Array.new
while array_size > 1
every_other_element.push(array_size - 2)
array_size -= 2
end

``````#debug
#puts "Every other element: #{every_other_element}"

#multiply each element by 2
touched_array = Array.new
every_other_element.each { |element|
``````

touched_array.push(@card_array[element].to_i*2) }

``````#debug
#puts "Touched array: #{touched_array}"

#split each into digits
split_touched_array = Array.new
touched_array.each { |e| split_touched_array.push(e.to_s.split(//))
``````

}
split_touched_array.flatten!

``````#debug
#puts "Split touched array:"
#puts split_touched_array

#return digits to integer form
split_touched_array_integers = Array.new
split_touched_array.each { |e|
``````

split_touched_array_integers.push(e.to_i)
}

``````#debug
#split_touched_array_total = 0
#split_touched_array_integers.each { |e| split_touched_array_total
``````

+= e
}
#puts “split total = #{split_touched_array_total}”

``````#concatentate the two arrays
all_digit_array = untouched_elements + split_touched_array_integers

#find the total value of the touched and untouched digits from the
``````

card
number
array_total_value = 0
all_digit_array.each { |x| array_total_value += x }

``````#debug
#puts "array total value = #{array_total_value}"

#final determination of validity by Luhn algorithm
@numerical_validation = false

if array_total_value % 10 == 0
@numerical_validation = true
puts "This card number, #{@card_array}, is valid [by Luhn
``````

algorithm]"
else
puts “This card number, #{@card_array}, is in-valid [by Luhn
algorithm]”
end

end

end

my_card = CardValidator.new
my_card.get_card_number
my_card.validate_card_prefix
my_card.validate_luhn

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