Hanoi

Haskellでハノイの塔を解く。
書籍、「C言語によるはじめてのアルゴリズム入門」の内容をそのまま落とし込みました

type Disk = Int
type Disks = (Int,[Disk])
type Pillar = [Disks]

hanoi :: Int -> Pillar ->IO()
hanoi 0 _ = return ()
hanoi n [(a,p1),(b,p2),(c,p3)] =
    do hanoi (n-1) [(a,p1),(c,p3),(b,p2)]
       print str
       hanoi (n-1) [(c,p3),(b,p2),(a,p1)]
  where
    str = show n++"was moved from "++show a++" to "++show b

dataSet :: Int -> Pillar
dataSet n = zip [1..3] $ take n [1..] : [[0],[0]]

main = do n <- getLine
          hanoi (read n).dataSet $ read n

はじめにあるtype宣言は、円盤の大きさから柱の状態を表すためのもの

実行結果は以下のよう

$>hanoi
3
"1was moved from 1 to 2"
"2was moved from 1 to 3"
"1was moved from 2 to 3"
"3was moved from 1 to 2"
"1was moved from 3 to 1"
"2was moved from 3 to 2"
"1was moved from 1 to 2"

ただこれでは寂しいので、ちゃんと遷移の様子が分かるようにしたいのだけれど...