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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.
Like this solution even better than mine!
As a note, you don't HAVE to use a regex to solve this. It's the method I chose to implement in my solution but there are other ways.
Actually the first two test cases involving 1.2.3.4 are NOT valid and the last is. Hint: an IP can consist only of digits and periods.