Its not very scientific – but I’d suggest writing a unit test that creates a list of items with random locations, add those items to your KdTree, and then remove one item at a time from both the list and the tree. Then you can ensure that removal works using CollectionAssert. It does not guarantee correctness, but it will quickly catch big issues.

My implementation is also hardened to support two items with the same location (and removal of a specific one). But I have simple equality rules – so that was easy to implement for me.

Its not very scientific – but I’d suggest writing a unit test that creates a list of items with random locations, add those items to your KdTree, and then remove one item at a time from both the list and the tree. Then you can ensure that removal works using CollectionAssert. It does not guarantee correctness, but it will quickly catch big issues.

My implementation is also hardened to support two items with the same location (and removal of a specific one). But I have simple equality rules – so that was easy to implement for me.

Regarding both bugs, I think I’ve managed to fix them now. Your suggested change for the first issue seems to make sense, so I’ve included that verbatim. The second wasn’t too tricky, but you can have a look at that too.

Cheers, A.

Maybe you could post a reproduction case for the second possible bug? One for the first would be appreciated either; for unit tests, but I should be able to do that anyway.

You need to make sure you return the SMALLEST of leftMinValue and rightMinValue. So you need to compare them to each other. Right now, you favor leftMinValue.

This can corrupt the tree because you may copy a node up to the pivot that does not respect the splittingDimension (return node.Value).

BROKEN CODE:
if (node.LeftChild == null && node.RightChild == null)
return null;

if (node.RightChild != null)
{
node.Value = FindMinimum(node.RightChild, dimension, depth + 1);
}
else
{
node.Value = FindMinimum(node.LeftChild, dimension, depth + 1);
node.LeftChild = null;
}

node.RightChild = Remove(node.Value, node.RightChild, depth + 1);

FIXED CODE:
if (node.RightChild != null)
{
node.Value = FindMinimum(node.RightChild, dimension, depth + 1);
node.RightChild = Remove(node.Value, node.RightChild, depth + 1);
}
else if (node.LeftChild != null)
{
node.Value = FindMinimum(node.LeftChild, dimension, depth + 1);
node.RightChild = Remove(node.Value, node.LeftChild, depth + 1);
node.LeftChild = null;
}
else
{
node = null;
}