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);

When I removing node '5' from the binary tree, it show error that 'Cannot read property 'element' of undefined' but when i deleting the node '3' from the binary tree the it not showing me error, on that time the code works properly and deleting the node '3' perfectly.

enter code here

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);

output: for removing node 5 from the binary tree

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

output: for removing node 3 from the binary tree.

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

Answer 1

The problem is in findMinNode method. You probably forgot to add return inside the else statement:

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