Compute Ackermann function

gistfile1.txt

def ack(m, n):
  stack = [(m, 1)]
  while len(stack):
    m, c = stack.pop()
    if m == 0:
      n += c
    elif m == 1:
      n += 2 * c
    elif m == 2:
      n = 2**c * (n + 3) - 3
    else:
      if c >= 2:
        stack.append((m, c - 1))
      stack.append((m - 1, n + 1))
      n = 1
  return n