[OTHER] Cleanup classes with very strange design

[vil02]

What would you like to share?

There are probably many classes in this repository, which have some strange design - we should update all of them. I think we can start with cleaning up these:

List of the classes needing redesign:

• AllPathsFromSourceToTarget
• ArrayCombination (refactor: redesign ArrayCombination #5181 by @yuvashreenarayanan3)
• Combination
• ColumnarTranspositionCipher
• StringMatchFiniteAutomata
• LetterCombinationsOfPhoneNumber

(@siriak, @BamaCharanChhandogi feel free to edit the list above)

Additional information

How to contribute

1. select one class form the list above such that no one else is working on (and is not done yet),
2. write a comment "Hey, I am working on XYZ", where XYZ is your selected class,
3. in your fork, please create a branch like cleanup_XYZ,
4. make your changes and create a pull-request, in which you mention this issue by writing something like "Related to #(this issue number)". Please make sure that you add all necessary tests. If possible, prefer parametrized tests.

Also feel free to suggest a class, which should be added to the list above.

[yuvashreenarayanan3]

Hey, I am working on "ArrayCombination"