parsing numbers in a string - ruby

Question

I'm trying to get my code to pass this test. If you've ever played magic the gathering, this might look familiar to you.
Test.assert_equals(can_cast("11RB","10B","1R"), true)
Test.assert_equals(can_cast("13BBRR","10BR","2R","B"), true)
But I can't seem to parse the correct numbers out of the elements correctly. Does anyone see a flaw in my code that's keeping me from passing these test?
def can_cast(hand, *spell_cost)
colored_mana_hand = Array.new
colored_mana_cost_aggregate = Array.new
colored_mana_spent = Array.new
colorless_mana_hand_array = []
colorless_mana_hand = 0
colorless_mana_cost_array = []
colorless_mana_cost_aggregate_array = []
colorless_mana_cost_aggregate = 0
hand.split("").each do |i|
if i.to_i != 0 # extracting existing colorless mana from hand
colorless_mana_hand_array << i
else
colored_mana_hand << i
end
end
colorless_mana_hand = colorless_mana_hand_array.join.to_i
spell_cost.each do |i| # extracting existing colorless mana from cost
i.split("").each do |j|
if j.to_i != 0
colorless_mana_cost_array << j
else
colored_mana_cost_aggregate << j
end
end
colorless_mana_cost_aggregate_array << colorless_mana_cost_array.join
colorless_mana_cost_array.clear
end
colorless_mana_cost_aggregate_array.each do |i|
colorless_mana_cost_aggregate += i.to_i
end
colored_mana_cost_aggregate.each do |i| # pay colored mana first
if colored_mana_hand.include?(i)
colored_mana_spent << i
colored_mana_hand.rotate(colored_mana_hand.index(i)).shift
end
end
(colored_mana_spent.sort == colored_mana_cost_aggregate.sort) && (colored_mana_hand.length + colorless_mana_hand) >= colorless_mana_cost_aggregate
end

Answer 1

This is a funny way to pull numbers out of the string. It would probably be easier to use scan, here is how you can use it:
# extracting existing colorless
colorless_mana_hand_array = hand.scan(/\d/).join.to_i
This will extract the digits from the string into an array, join them, and then convert to an integer.

Answer 2

Does anyone see a flaw in my code that's keeping me from passing these test?
Yes, Indeed.
You split your spell_cost strings via:
i.split("").each do |j|
# ...
end
The code will yield each single character to the block. For "10BR" this gives:
"10BR".split("").each do |j|
p j: j
end
Output:
{:j=>"1"}
{:j=>"0"}
{:j=>"B"}
{:j=>"R"}
Furthermore you have this check:
if j.to_i != 0
colorless_mana_cost_array << j
else
colored_mana_cost_aggregate << j
end
For the above input, you get
colorless_mana_cost_array #=> ["1"]
colored_mana_cost_aggregate #=> ["0", "B", "R"]
Because "0".to_i != 0 evaluate to false, just like "B" and "R".
If I understand your code correctly, "0" should go into the colorless_mana_cost_array.