从二叉树中删除节点时遇到问题？

Question

class Node{
 constructor(element){
    this.element = element;
    this.right = null;
    this.left = null;
 }
}

class BST{
 constructor(){
    this.head = null;
 }

 add(element){
    var node = new Node(element);

    if(this.head === null){
        this.head = node;
    }else{
        this.insertNode(this.head,node);
    }
 }
 insertNode(node,key){
    if(key.element < node.element){
        if(node.left === null){
            node.left = key;
        }else{
            this.insertNode(node.left,key);
        }
    }else{
        if(node.right === null){
            node.right = key;
        }else{
            this.insertNode(node.right, key);
        }
    }
 }

 remove(element){
    this.head = this.removeNode(this.head,element);
 }
 removeNode(node,key){
    if(node === null){
        return null;
    }else if(key < node.element){
        node.left = this.removeNode(node.left,key);
        return node;
    }else if(key > node.element){
        node.right = this.removeNode(node.right,key);
        return node;
    }else{
        if(node.left === null && node.right === null){
            node = null;
            return node;
        }
        if(node.left === null){
            node = node.right;
            return node;
        }else if(node.right === null){
            node = node.left;
            return node;
        }
        var temp = this.findMinNode(node.right);
        node.element = temp.element;

        node.right = this.removeNode(node.right, temp.element);
        return node;

    }
 }

 findMinNode(node){
    if(node.left === null){
        return node;
    }else{
        this.findMinNode(node.left);
    }
 }
 }

 var bst = new BST();
 bst.add(10);
 bst.add(5);
 bst.add(3);
 bst.add(7);
 bst.add(4);
 bst.add(2);
 bst.add(6);
 bst.add(9);
 bst.add(8);
 bst.add(15);
 bst.add(24);
 bst.add(22);
 bst.add(25);
 bst.add(21);
 bst.remove(3);
 console.log(bst);

当我从二叉树中删除节点'5'时，它显示错误'无法读取未定义的属性'element'，但是当我从二叉树中删除节点'3'时，它不显示我错误，那时代码可以正常工作，并且可以完美删除节点“ 3”。

在此处输入代码

class Node{
 constructor(element){
    this.element = element;
    this.right = null;
    this.left = null;
 }
}

class BST{
 constructor(){
    this.head = null;
 }

 add(element){
    var node = new Node(element);

    if(this.head === null){
        this.head = node;
    }else{
        this.insertNode(this.head,node);
    }
 }
 insertNode(node,key){
    if(key.element < node.element){
        if(node.left === null){
            node.left = key;
        }else{
            this.insertNode(node.left,key);
        }
    }else{
        if(node.right === null){
            node.right = key;
        }else{
            this.insertNode(node.right, key);
        }
    }
 }

 remove(element){
    this.head = this.removeNode(this.head,element);
 }
 removeNode(node,key){
    if(node === null){
        return null;
    }else if(key < node.element){
        node.left = this.removeNode(node.left,key);
        return node;
    }else if(key > node.element){
        node.right = this.removeNode(node.right,key);
        return node;
    }else{
        if(node.left === null && node.right === null){
            node = null;
            return node;
        }
        if(node.left === null){
            node = node.right;
            return node;
        }else if(node.right === null){
            node = node.left;
            return node;
        }
        var temp = this.findMinNode(node.right);
        node.element = temp.element;

        node.right = this.removeNode(node.right, temp.element);
        return node;

    }
 }

 findMinNode(node){
    if(node.left === null){
        return node;
    }else{
        this.findMinNode(node.left);
    }
 }
 }

 var bst = new BST();
 bst.add(10);
 bst.add(5);
 bst.add(3);
 bst.add(7);
 bst.add(4);
 bst.add(2);
 bst.add(6);
 bst.add(9);
 bst.add(8);
 bst.add(15);
 bst.add(24);
 bst.add(22);
 bst.add(25);
 bst.add(21);
 bst.remove(5);
 console.log(bst);

输出：用于从二叉树中删除节点5

 node.element = temp.element;
                    ^
 TypeError: Cannot read property 'element' of undefined

输出：用于从二叉树中删除节点3。

 BST {
  head: Node {
  element: 10,
  right: Node { element: 15, right: [Node], left: null },
  left: Node { element: 5, right: [Node], left: [Node] }
  }
 }

Answer 1

问题出在findMinNode方法中。您可能忘记了在return语句中添加else：

  findMinNode(node) {
    if (node.left === null) {
      return node;
    } else {
      // return the value of recursive call
      return this.findMinNode(node.left);
    }
  }