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35 lines
1.2 KiB
Haskell
35 lines
1.2 KiB
Haskell
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{- mbinary
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#########################################################################
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# File : BFS_knight.hs
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# Author: mbinary
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# Mail: zhuheqin1@gmail.com
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# Blog: https://mbinary.coding.me
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# Github: https://github.com/mbinary
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# Created Time: 2018-11-11 19:40
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# Description:
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#########################################################################
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-}
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{-
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Given two different positions on a chess board, find the least number of moves it would take a knight to get from one to the other. The positions will be passed as two arguments in algebraic notation. For example, knight("a3", "b5") should return 1.
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The knight is not allowed to move off the board. The board is 8x8.
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-}
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module ShortestKnightPath.Kata (knight) where
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import Data.Char
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import Data.List
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knight :: String -> String -> Int
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knight s1 s2 = let begin = axis s1
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end = axis s2
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notEnd = all (\tp->tp /=end)
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in length . takeWhile notEnd .iterate gen $[begin]
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gen li = nub. flatten $map (filter (\(a,b) ->a>0 && b>0 &&a<9&&b<9 ) . change) li
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change (a,b) = [(a-1,b-2),(a-1,b+2),(a+1,b-2),(a+1,b+2),(a+2,b-1),(a+2,b+1),(a-2,b+1),(a-2,b-1)]
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axis s = (ord (s!!0) -96, digitToInt (s!!1)::Int)
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flatten [] = []
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flatten (x:xs) = x ++ flatten xs
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