If you don't mention any attribute the problem will be completely random in that attribute. For example if you don't choose any rating, random ratings will appear. Choosing no attribute (i.e. no specification in tags, index, rating) will make the problem completely random
If you choose dp and greedy from tags and 1000 from rating, a random problem with a tag of 'dp' or 'greedy' (or both!) which has a rating of 1000 will be shown.
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