Keep in mind that I’m not saying that C++ is a better language than Go here: I’d need a lot more evidence than an array deduplication routine to prove this. I’m just saying that Go is ill-suited for this particular task as compared to C++, and the author is struggling with this as they go through with implementing their algorithm; this leads them to settle on a clumsy and inefficient “solution” because there isn’t really a good alternative in the confines of the language that they chose. (FWIW, C++ does have a good standard library for implementing algorithms but this doesn’t really come into play here, since we’re not doing anything advanced. Any language with a set and filter would do the job. And for the record, I do think that C++ is a better language than Go, but I’m not going to argue it here because I don’t know the latter well enough to be confident in my viewpoint and don’t have enough space here to discuss it here if I did.)