Challenge questions in long challenges

I would like to know about the challenge questions in the long challenges. How are they judged, and why are the submissions of these questions continuously re-judged?

@harshvk5 challenge problems have scoring mechanism which is pre-defined in the problem itself.
The challenge problem either maximizes or minimizes the final score and according to it the points are given.

The best solution gets 1pts and others are given scores relative to it.