What should be returned by the remove method of the BinarySearchTreeNode?

[m-maksyutin]

Hi! The remove method returns a BinarySearchTreeNode object. But there is one uncertain moment. What should be contained in the properties of this object, such as the parent, left, right? Are these properties relevant? Or they must be null?

[intern0t]

It should be relevant, it is setting a delimiter whether to continue, fall back or if nodeToRemove is actually the last one. The question about whether it must be null depends on the properties left and right. If right is null, that means there are no nodes beyond the current one, nodeToRemove and is the last one.

Sorry, if I am not clear enough.

[m-maksyutin]

Thanks for the explanation, @intern0t .

For clarity, please specify these things:

Should these properties of the returned object correspond to the tree state before the node is deleted or after?

For example, is it correct to change the right property here?

javascript-algorithms/src/data-structures/tree/binary-search-tree/BinarySearchTreeNode.js

Line 111 in 9de6bc7

nodeToRemove.right = nodeToRemove.right.right;

Same question to the value property:

javascript-algorithms/src/data-structures/tree/binary-search-tree/BinarySearchTreeNode.js

Line 106 in 9de6bc7

nodeToRemove.value = nextBiggerNode.value;

javascript-algorithms/src/data-structures/tree/binary-search-tree/BinarySearchTreeNode.js

Line 110 in 9de6bc7

nodeToRemove.value = nodeToRemove.right.value;

Also, if you add this check to the BinarySearchTreeNode.test.js, it will fail:

it('should return removed node containing a value that should have been deleted', () => {
  const bstRootNode = new BinarySearchTreeNode();
  bstRootNode.insert(10);
  bstRootNode.insert(20);
  bstRootNode.insert(30);
  bstRootNode.insert(15);

  const removedNode1 = bstRootNode.remove(20);
  expect(removedNode1.value).toBe(20);
});

[rakshithjk]

I think that properties of the returned object correspond to the tree state before the node is deleted.

110. nodeToRemove.value = nodeToRemove.right.value;

You have changed the value of nodeToRemove with the value that has to be replaced (in the example you have mentioned, 30).Now when you return nodeToRemove.value it would return 30 whereas 20 was expected. Instead return parent

[trekhleb]

Yes, you right @m-maksyutin, there is an uncertainty in removal method. To avoid similar confusion I've changed the code so that removal method will return boolean (whether node has been successfully deleted or not). Because returning the node truly brings confusion about its value, left, right and parent properties.