Scala Pattern Matching Demo

pattern.scala

sealed abstract class BinaryTree
case class BinTreeLeaf(value: Int) extends BinaryTree
case class BinTreeNode(left: BinaryTree, right: BinaryTree) extends BinaryTree

def leafSum(tree: BinaryTree): Int = tree match {
 case node: BinTreeNode => leafSum(node.left) + leafSum(node.right)
 case leaf: BinTreeLeaf => leaf.value
}

"Method leafSum" should "traverse a binary tree in order" in {
  /**
  *       .
  *   .       .
  * 1   3   7   5
  */
  val BinaryTree = BinTreeNode(BinTreeNode(BinTreeLeaf(1), BinTreeLeaf(3)), BinTreeNode(BinTreeLeaf(7), BinTreeLeaf(5)))

  leafSum(BinaryTree) should be(16)
}