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Solving LinkedIn Queens with APL

14 Jun 2025 on Peter Vernigorov’s blog A couple months ago I noticed that LinkedIn now has a few simple games. They’re not much to write home about, but I really enjoy playing Queens.

Both were quite interesting to me, so I thought this was a good opportunity to also solve the game in my favourite language - APL - and share my experience. The default is 1-based; however, the place function doesn’t work there for surprisingly complicated reasons - it involved the behaviour of Each with empty lists, prototypes, and@ primitive failing when asked to update index (0,0) in 1-based origin system. Last line in this function implicitly returns the result - list of legal positions for a queen in the color region.

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