Not to be a pain here, but this code is a perfect example of how to grossly complicate something that is reasonably simple.
Just for starters, converting the numbers to strings and then using regular expressions is just wrong. When you're dealing with numbers, you have to deal with them *as* numbers. Changing them to strings will do nothing but add awkwardness and complication to the algorithm.
Second, it is not necessary to actually *create* the string in order to calculate it's length.
Third, your method `runProblem` is a perfect example of when *NOT* to use a list because a plain, ord…