In #549, we added unittests for dispatch AtCoder and Codeforces.
To increasing test coverage, we should add unittests for other contest (HackerRank, CS Academy, ...).

Not only tests for all other contests, tests for the part of contests are welcome.

There are two sets of refactoring that can be performed on our codebase to make them more efficient and utilize the full potential offered by Qt Framework. See below:

1. There is no need to explicitly call delete on widgets that are allocated on Heap as long as in their constructor we have specified the parent widget for it. Consider this example below:

class Widget: public QObject

I think it would be a good idea if we could choose CF tags(like dp, geometry, etc.) for duels, but choosing tags made the duel unofficial.