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object james_bond_jr { | |
type State = Vector[Int] | |
val initialState: State = Vector(1,2,2,1, 3,4,4,3, 3,4,4,3, 2,4,4,2) | |
val endState: State = Vector(4,3,4,2, 3,1,2,4, 4,2,4,3, 2,4,3,1) | |
trait Move { | |
def act(state: State): State | |
} | |
case class MoveLeft(row: Int) extends Move { | |
def act(state: State) = state.updated(0 + row * 4, state(1 + row * 4)).updated(1 + row * 4, state(2 + row * 4)).updated(2 + row * 4, state(3 + row * 4)).updated(3 + row * 4, state(0 + row * 4)) | |
} | |
case class MoveRight(row: Int) extends Move { | |
def act(state: State) = state.updated(1 + row * 4, state(0 + row * 4)).updated(2 + row * 4, state(1 + row * 4)).updated(3 + row * 4, state(2 + row * 4)).updated(0 + row * 4, state(3 + row * 4)) | |
} | |
case class MoveUp(col: Int) extends Move { | |
def act(state: State) = state.updated(0 + col, state(4 + col)).updated(4 + col, state(8 + col)).updated(8 + col, state(12 + col)).updated(12 + col, state(0 + col)) | |
} | |
case class MoveDown(col: Int) extends Move { | |
def act(state: State) = state.updated(4 + col, state(0 + col)).updated(8 + col, state(4 + col)).updated(12 + col, state(8 + col)).updated(0 + col, state(12 + col)) | |
} | |
val moves = | |
(for (i <- 0 until 4) yield MoveLeft(i)) ++ | |
(for (i <- 0 until 4) yield MoveRight(i)) ++ | |
(for (i <- 0 until 4) yield MoveUp(i)) ++ | |
(for (i <- 0 until 4) yield MoveDown(i)) | |
class Path(path: List[Move], val endState: State) extends Ordered[Path]{ | |
def extend(move: Move) = new Path(move :: path, move act endState) | |
override def toString = (path.reverse mkString " ") + "-->" + endState | |
def compare(that: Path): Int = { | |
def diffFromEnd(x:Path) :Int = (x.endState zip endState).count( {case (x,y) => x!=y} ) | |
diffFromEnd(this) - diffFromEnd(that) | |
} | |
} | |
val initialPath = new Path(Nil, initialState) | |
def from(paths: Vector[Path], explored:Set[State]): Stream[Vector[Path]] = { | |
if (paths.isEmpty) Stream.empty | |
else { | |
val more= for { | |
path <- paths | |
next <- moves map path.extend | |
if !(explored contains next.endState) | |
} yield next | |
//val a = println("pathSet.size =" + more.size + "explored.size = " + explored.size) | |
val sortedMore = (more take 50000).sorted | |
paths #:: from(sortedMore, explored ++ (sortedMore map (_.endState))) | |
} | |
} | |
val pathSets = from(Vector(initialPath), Set(initialState)) | |
def solution = { | |
for { | |
pathSet <- pathSets | |
path <- pathSet | |
if path.endState == endState | |
} yield path | |
} | |
def printSolution(p: Stream[Path]): Unit = { | |
val l = (solution take 1).toList | |
println(l mkString "\n") | |
return | |
} | |
printSolution(solution) | |
} |
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