Phone numbers out of chess moves

phones.scala

package interview

object DominoInterview extends App {
	/**
	|1|2|3|
	|4|5|6|
	|7|8|9|
	|*|0|#|

	Problem:
	Given a chess piece and a starting position
	Making only legal chess moves find all valid 7 digit phone numbers

	Example: Knight starts at 1
	Some possible prefixes: 167, 183, 161, etc.
	*/

	val validMoves = Map(
		1 -> List(6, 8),
		2 -> List(9, 7),
		3 -> List(4, 8),
		4 -> List(3, 9, 0),
		5 -> List(),
		6 -> List(7, 1),
		7 -> List(2, 6),
		8 -> List(3, 1),
		9 -> List(4, 2),
		0 -> List(4, 6)
	)
  
  // I guess by passing a different Map we can generalize over all pieces

	def getPhoneNo(start: Int, acc: List[Int]): List[Int] = {
		if (acc.size == 7) acc
		else {
			val l: List[Int] = validMoves.get(start).get
			l.flatMap { e => getPhoneNo(e, acc :+ e) }
	  }
	}

	def group(list: List[Int], acc: List[List[Int]]): List[List[Int]] = {
		if (list.isEmpty) acc
		else {
			group(list.slice(7, list.length), list.take(7) :: acc)
		}
	}

	group(getPhoneNo(1, List()), List.empty[List[Int]]).foreach(println)
}