Loading collection data...
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.
Harder test could be added to make it worth it to solve efficiently. Creating another kata where a slow solution doesn't pass the tests may be also interesting.
You may not a beginner anymore, but I think the complexity of this is O(n^2) where n is the len of the secret.