> The solution is surprisingly simple: we can store every node in a dynamic array, (a Vec in Rust) and use indices into this vector to refer to other nodes. Thi

> The solution is surprisingly simple: we can store every node in a dynamic array, (a Vec in Rust) and use indices into this vector to refer to other nodes. This solves the ownership problem because the vector now owns all the nodes. And by simply storing the index of the parent in every node we can navigate the tree in both directions without having to use any unsafe code. > This all hinges on the assumption that once we’ve inserted a node into the vector its index never changes. Inserting new nodes doesn’t cause any issues: we just append them to the end. Removing a node however would be doubly bad: not only is it a linear operation (because we’re now using a vector instead of a tree), but it would also invalidate all the indices of the nodes that come after it. If you use my crate slotmap (https://docs.rs/slotmap/latest/slotmap/ https://docs.rs/slotmap/latest/slotmap/) you can support deletions without worrying about indices shifting or 'indices' (slotmap calls them keys) ever pointing at different values, as the keys in slotmap also come with a version number.