骑士问题

gistfile1.scala

问题描述，有一个横8纵8的国际象棋棋盘，也就是坐标x,y都在（1..8)的范围内。
在棋盘的任意坐标上放一个马，马的走步规则，跟中国象棋差不多。。。如果不了解的话请谷歌之
现在给定棋盘上任意坐标，问这个马是否有可能精确的在第3步上走到该坐标？

=======================下面的解法译自haskell==================================
def moveKnight: (Int,Int) => List[(Int,Int)] = (c,r) => { 
  List((c+2,r-1),(c+2,r+1),(c-2,r-1),(c-2,r+1),
       (c+1,r-2),(c+1,r+2),(c-1,r-2),(c-1,r+2)) filter (pos => (1 to 8).contains(pos._1) && (1 to 8).contains(pos._2))
}

val moveKnightT = moveKnight.tupled

def in3: (Int,Int) => List[(Int,Int)] = (x,y) => { 
  List((x,y)) flatMap moveKnightT flatMap moveKnightT flatMap moveKnightT
}

def canReachIn3: (Int,Int) => (Int,Int) => Boolean = (startX,startY) => (endX,endY) => { 
  in3(startX, startY) contains (endX,endY)
}

===================test case ============================
scala> canReachIn3(6,2)(6,1)
res0: Boolean = true

scala> canReachIn3(6,2)(7,3)
res1: Boolean = false

good