TST's deletion is buggy

[nbro]

After visualizing the behaviour of a TST data structure using this tool, I realized that my implementation of deletion is buggy.

_delete_fix keeps deleting nodes up to the root and while u has no children, but it doesn't consider the fact that the current node u may contain a value and thus is not to be deleted.

This may not be the only problem... !! I need to think about all possible cases very well. Have a look at the implementation by galles.

[nbro]

The way the implementation of the TST of Galles works is slightly different than my implementation.

I think I solved the problem, but by modifying my function, rather than taking into consideration his implementation.