blah.rb

def replace(s, casey)
  a = s
  case casey
  when 1
    a.sub("AB", "AA")
  when 2
    a.sub("BA", "AA")
  when 3
    a.sub("CB", "CC")
  when 4
    a.sub("BC", "CC")
  when 5
    a.sub("AA", "A")
  when 6
    a.sub("CC", "C")
  end
end


def solution(s)
  funcs = (1..6).to_a
  cont = true
  while cont do
    count = 1
    for i in funcs
      s2 = replace(s, i)
      count = count + 1
      if s2 != s
        puts s2
        puts i
        funcs.delete(i)
        s = s2
        break
      end
      if count == funcs.length
        cont = false
        break
      end
    end
    s
  end
end

puts solution("ABBCC")