Random tests in C# expect 0 for start == end cases which is wrong as the answer should be the value of start (already raised as an issue numerous times)

bro you wont die from typing out args 1 time

Not a suggestion.

If you can write a brute-force solution (that will pass up to sample test 6) I think you've perfectly understood the descriptions ;-)

best

Just completed some tests on both versions (cased and if elsed) for 10,000,000 iterations ifed took on average 3745820 ticks and cased for same tests took on average 3565270 ticks so realy is no diference. I think you are right Voile :) I have to aggre whit you this time :)

Yep I think this one is best

:)

And Arphox I think your solution is not that good to :) string builder is good choise only if strings are big or is many of them like milion or so. In this case Concat or string join something like this or even aggregate is better choise when building small string.

Yes this solution is not the best performance wise its jus simple one :)