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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.
sound reasonable. I would check it again
My O(n) solution got time out error. LOL! Just 1 failure case because of time out error and I cannot submit my solution.
So many wrong test cases, they made me feel so annoyed when I had to check again so many times and found that it is the problem of test cases.
the test case is wrong, I tried by my hand and found it wrong