@input = File.read("5.input").split("\n")
@instrs = @input.filter{|line| line.include?("move")}.map{|line| line.split(/[a-z ]+/)}

def run_part
  stacks = @input.filter {|line| line.include?("[")}.map{|line| line.chars.each_slice(4).to_a.map{|block| block[1]}}.transpose.map{|stack| stack.filter{|box| box != " "}.reverse}

  @instrs.each do |inst|
    (_, cnt, from, to) = inst.map{|i| i.to_i}
    yield stacks, cnt, from - 1, to - 1
  end

  puts stacks.map{|s| s[-1]}.join()
end

# Part 1
run_part do |stacks, cnt, from, to|
  (1..cnt).each do |_|
    box = stacks[from].pop()
    stacks[to].append(box)
  end
end

# Part 2
run_part do |stacks, cnt, from, to|
  boxes = stacks[from].pop(cnt)
  stacks[to] = stacks[to].concat(boxes)
end