Created
November 14, 2018 08:55
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| [STAThread] | |
| static void Main(string[] args) | |
| { | |
| while(true) | |
| { | |
| Console.WriteLine("ID?"); | |
| var id = Console.ReadLine(); | |
| Console.WriteLine(Decrement(id)); | |
| } | |
| } | |
| private static readonly char[] ValidChars = new char[] | |
| { | |
| 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', | |
| 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', | |
| 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', | |
| '0', '1', '2', '3', '4', '5', '6', '7', '8', '9' | |
| }; | |
| private static string Decrement(string id) | |
| { | |
| var idChars = id.ToCharArray().Reverse(); | |
| var newId = new List<char>(); | |
| bool wrapNext = true; | |
| foreach (var c in idChars) | |
| { | |
| if (wrapNext) | |
| { | |
| var newC = Previous(c); | |
| newId.Add(newC); | |
| wrapNext = newC == ValidChars[ValidChars.Length - 1]; | |
| } | |
| else | |
| { | |
| newId.Add(c); | |
| } | |
| } | |
| newId.Reverse(); | |
| return new string(newId.ToArray()); | |
| } | |
| private static char Previous(char c) | |
| { | |
| var i = Array.IndexOf(ValidChars, c) - 1; | |
| return ValidChars[i < 0 ? ValidChars.Length - 1 : i]; | |
| } |
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