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Collections are a way for you to organize kata so that you can create your own training routines. Every collection you create is public and automatically sharable with other warriors. After you have added a few kata to a collection you and others can train on the kata contained within the collection.
Get started now by creating a new collection.
IMO there should be another 2 or 3 digit number in the examples. You can very easily get a pattern that works beautifully with the displayed cases, but then falls apart on the attempt. Took me a minute, but this was a really fun problem.
Should this be a 6kyu? I feel like it was a 7 or 8.
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I love how you took this functional programming problem and turned it into a Data problem. It really is more efficient than any other way when you think about it
I'm not sure this is an efficient solution, the problem is that you are iterating through potentially the entire list twice. Lets say 90% of a million user list uses JavaScript, but only 10% of those are from Europe. You will iterate through 900K people twice with each filter. Or instead you could add an && statement there and knock it all out in one go.