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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.
This is a 3 kyu kata. You can't expect your naive solution to work. There is a reason it's 3 kyu.
Linear time solutions are likely too slow for this kata.
And your solution seems to be exponential time.
Read SICP for a good resource on these types of questions.