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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.
The best practice is to never write this kind of solution. Ever.
Look at the top solutions using a stack.
Looks cool and concise but not efficient with the string lookups :(
Simply and pretty but b should be converted to a set first for O(n) performance