List("apple banana", "orange apple mango", "kiwi papaya orange","mango orange muscat apple") に含まれるフルーツの数を数える関数 countFruitsFromLines を実装せよ。
val lines = List("apple banana", "orange apple mango", "kiwi papaya orange","mango orange muscat apple")
val fruitsCounts = countFruitsFromLines(lines)
if (fruitsCounts == Map("banana" -> 1, "muscat" -> 1, "orange" -> 3, "mango" -> 2, "apple" -> 3, "kiwi" -> 1, "papaya" -> 1)){