Or anywhere in the EU. And I don't think the USA is more lenient on piracy. But perhaps they are if a big company is the one doing it.

Why? They immediately explain that the difference in performance would not be significant on such a small problem and I see no other reason to prefer arrays over maps.

Also, I think the 'find' operation could be replaced by an operation that checks if two elements are in the same set. That way you don't have to come up with a "name".

One thing I'm missing is which problems this technique can solve. I believe one important use case is in type inference. Are there many other problems that can be solved by union-find?