Java二进制搜索树递归副本树 [英] Java Binary Search Tree Recursive Copy Tree

问题描述

我正在解决一个问题，该问题要求我递归复制二进制搜索树并返回该树.我在二进制搜索树类中进行编码，因此它将复制它被调用的任何二进制搜索树.要求说私有方法必须具有返回类型Entry<E>和参数类型Entry<E>.我遇到的问题是将多个条目添加到树中.

I'm working on a problem which requires me to copy a binary search tree recursively and to return the tree. I am coding in the binary search tree class, so it will copy whatever binary search tree it is called on. The requirements say that the private method must have a return type of Entry<E> and a parameter of type Entry<E>. The problem I'm running into is getting multiple entries added to the tree.

这是我目前拥有的:

public BinarySearchTree<E> rcopy(){
   BinarySearchTree newTree = new BinarySearchTree();
   newTree.add(rcopy(root).element);
   return newTree;
}


private Entry <E> rcopy(Entry <E> current){
   if(current.left!=null) return rcopy(current.left);
   if(current.right!=null) return rcopy(current.right);
   return current;
}

这是Entry类，所以您知道我可以得到的东西:

And here is Entry class so you know what I have available to me:

protected static class Entry<E> {
    protected E element;
    protected Entry<E> left = null,
                       right = null,
                       parent;
    protected int  pos;
protected Entry<E> link = null;
public Entry() { }
    public Entry (E element, Entry<E> parent) 
{
       this.element = element;
       this.parent = parent;
    }
}

推荐答案

private Entry <E> rcopy(Entry <E> current){
   if(current.left!=null) return rcopy(current.left);
   if(current.right!=null) return rcopy(current.right);
   return current;
}

这不会复制任何内容.它将返回当前节点的最左侧(如果没有左侧子节点，则为最右侧；如果是叶节点，则为当前节点).因为您总是返回电流.您需要类似的东西:

This will not copy anything. It will return the left-most ( or right-most, if no left child; or current, if it is a leaf node ) child of the current node. Because you always return current. You need somelthing like:

private Entry <E> rcopy(Entry <E> current){
    if (current == null) return null;
    return new Entry <E> (current.element, rcopy(current.left), rcopy(current.right)); //write a constructor for that
 }

并实际上复制节点.我尚未测试代码，但为时已晚，希望它仍然正确.

and actually copy the nodes. I haven't tested the code and it is bit late, hope it is still correct.

您是否有理由区分BinarySearchTree<E>和Entry<E>?树的一部分不是树吗?

Is there a reason you distinguish between BinarySearchTree<E> and Entry<E>? Isn't a part of the tree also a tree?

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