Question

我目前正在尝试使用scala实现霍夫曼算法。为此，我想我会根据它们的权重使用PriorityQueue来排序树中不同节点的顺序。因此，我必须创建BinarySearchTree节点的PriorityQueue。但是，Scala只允许我按案例类的字段进行排序。

这是我想要的：

  class BinarySearchTree(weight: Int)
  case class ForkNode(left: BinarySearchTree, right: BinarySearchTree, chars: List[Char], weight: Int) extends BinarySearchTree(weight)
  case class LeafNode(char: Char, weight: Int) extends BinarySearchTree(weight)

  def createBST(inputFile: ListMap[Char,Int]): BinarySearchTree = {
    def weightOrder(t2: BinarySearchTree) = t2.weight
    val nodeMap:PriorityQueue[BinarySearchTree] = PriorityQueue(Ordering.by(weightOrder))
    null
  }

但它没有编译。但是，def weightOrder(t2: ForkNode) = t2.weight会编译，但这不是我想要的。

如何根据非案例类中的字段订购优先级队列？

Answer 1

这是不完整的但是编译。

let res1 = await get<storeA, 'category'>('/my/url1')
let res2 = await get<storeB, 'catList'>('/my/url2')

res1.data.category.category
res2.data.catList.categories

import scala.collection.immutable.ListMap import collection.mutable.PriorityQueue class BinarySearchTree(val weight: Int) //weight is now member data case class ForkNode( left: BinarySearchTree , right: BinarySearchTree , chars: List[Char] , override val weight: Int //now needs override ) extends BinarySearchTree(weight) case class LeafNode( char: Char , override val weight: Int //now needs override ) extends BinarySearchTree(weight) def createBST(inputFile: ListMap[Char,Int]): BinarySearchTree = { def weightOrder(t2: BinarySearchTree) = t2.weight val bst: BinarySearchTree = LeafNode('c',2) //build something of proper type val nodeMap:PriorityQueue[BinarySearchTree] = PriorityQueue(bst)(Ordering.by(weightOrder)) //create PriorityQueue null //etc. }是可变的并且类型不变，因此如果你想要PriorityQueue，那么构造函数参数必须是PriorityQueue[BinarySearchTree]类型而不是派生类型（即节点）。

通过非案例类的字段对PriorityQueue进行排序

1 个答案: