> Finally, deletes are hard in hash maps.
Deletes are hard in open hash maps like here; they're trivial in chained hash maps.
(I'm only posting this because this seems to be an exercise/learning-ish HN post and I think it's a relevant point to not forget.)
Right.
Thinking about it, I don't grasp why the author has opted for linear probing here. Given the amount of malloc(), they might have used linked lists as well.