c# Alpha Telephone Number Translator

Question

I have a homework assignment where the program will accept any phone number in the format similar to 555-GET-FOOD. The task is to map the alphabetic letters to numbers and tran

Answer 1

While "map" (implemented as Dictionary in C#/.Net) is probably best choice for this problem, basic math is enough for such simple transformation:

 Console.WriteLine(String.Join("",  // combine characters back to string
       "555-GET-FOOD" //value
          .ToUpperInvariant() // carefully converting to avoid Turkish I problems
          .Select(c=> (c>='A' && c<='Z') ? // only tweak A-Z range
             Math.Min((c-'A')/3+2,9).ToString()[0] : c)))