how do contributors create test cases such huge test cases ? I wish to contribute and wanna know the same .
I don’t think people can contribute in Test Set Generation. It’s the Problem setter (in rare cases tester may also) who generates Test Cases. Later, Testers test the Test Cases, Judging some factors like for example, whether the test set includes corner cases, whether brute-force solution will pass the test set, whether the test cases are according to the specified format and it obeys constraints etc.