refactor: 오목알을 놓을 수 있는지 확인하는 함수를 Players 클래스로 이동

src/main/kotlin/Board.kt

@@ -5,12 +5,8 @@ import player.Players
 class Board(private val players: Players) {
  constructor(blackPlayer: Player, whitePlayer: Player) : this(Players(blackPlayer, whitePlayer))
 
- private fun canPlace(stone: Stone): Boolean = allPlayers().none { it.isPlaced(stone) }
-
- private fun allPlayers(): List<Player> = players.toList()
-
  fun putStone(turn: Turn, stone: Stone): Player? {
- if (canPlace(stone)) {
+ if (players.canPlace(stone)) {
  return players.putStone(turn, stone)
  }
  return null

src/main/kotlin/player/Players.kt

@@ -6,7 +6,7 @@ import Turn
 class Players private constructor(private val players: Map<Turn, Player>) {
  constructor(black: Player, white: Player) : this(mapOf(Turn.BLACK to black, Turn.WHITE to white))
 
- fun toList(): List<Player> = players.values.toList()
-
  fun putStone(turn: Turn, stone: Stone): Player? = players[turn]?.putStone(stone)
+
+ fun canPlace(stone: Stone): Boolean = players.values.none { it.isPlaced(stone) }
 }