Scala 求和二叉树

Question

我在这里看到了 anwser，但我没有空对象，而且我在 Node 中不仅有叶子，还像这样： case class Node ( val e : Int ,left : BinaryTree, right : BinaryTree).

我在这个 def sums 中添加 Leaf 作为参数时遇到问题。

import scala.annotation.tailrec
 /**
 * @author emil
 */
 class tree {


 }


 sealed abstract class BinaryTree
 case class Node (left : BinaryTree, right : BinaryTree) extends BinaryTree
 case class Leaf (value : Int) extends BinaryTree


 object Main {
   def main(args : Array[String]) {
     val tree = Node(Node(Leaf(1),Leaf(3)), Node(Leaf(5),Leaf(7)));

     println(tree)

  sum(tree)

   }
  def sum(bin: BinaryTree) = {
  def sums(trees: List[BinaryTree], acc: Int): Int = trees match {
    case Nil => acc
    case Node(l, r) :: rs => sums(l :: r :: rs,  acc)
  }

  sums(List(bin),0)
}


}

Answer 1

如果我理解你想做的是

case Leaf(v) :: rs => sums(xs, acc+v)

Answer 2

可能是：

  def sum(bin: BinaryTree) = {
    def sums(t: BinaryTree): Int = t match {
      case Leaf(v)    => v
      case Node(l, r) => sums(l) + sums(r)
    }

    sums(bin)
  }

  val res = sum(tree)
  println(res) // 16

Scala 求和二叉树

Scala sum binary Tree

binary-tree

scala