module Homework.Ch01.TowerOfHanoi where

type Peg = String

type Move = (Peg, Peg)

hanoi :: Integer -> Peg -> Peg -> Peg -> [Move]
hanoi n x y z = runHanoi [] (reverse $ initStack n) [] []
  where
    initStack 0 = []
    initStack xx = xx : initStack (xx - 1)

    runHanoi moves (itemX : stackX) [] [] = runHanoi ((x, z) : moves) stackX [] [itemX]
    runHanoi moves (itemX : stackX) [] (itemZ : stackZ)
      | itemX > itemZ = runHanoi ((x, y) : moves) stackX [itemX] (itemZ : stackZ)
    runHanoi moves ()