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.
In your first loop, you only filter out items from a[] if they are at the same location as an item of the same value in b[]. That is not what the description specifies. Try reading it again.
And your second loop: I have no idea, what you're even attempting to do there, or why.