/* Odd-Even-Splitter strategies Attempt to adhere to SOLID principles. The menu class is build heavily on ideas I took from online example implementations of DI containers. The goal was to be able to extend the strategies with new ones while limiting the necessary edits to as few locations as possible. In this case, only a new command needs to be registered somewhere in the InitApp method. The input required is the method you want to use. Implemented strategies: linq - a Linq based splitter dblcount - a strategy counting odds and evens in a single run sglcount - a strategy counting only evens in a single run diff - Avoids if-else by calculating the difference between odds and evens More to follow :D */ using System; using System.Collections.Generic; using System.Linq; using System.Reflection; namespace AgnesAhlberg.OddEvenSplitter { using Library; namespace Library { #region Menu public class MenuItemNotFoundException : Exception { } public class Menu { private Dictionary _map = new Dictionary(); public void Register(T key, Type valueType) { _map.Add(key, valueType); } public V GetInstanceAs(T key) { if(_map.ContainsKey(key)) { Type _t = _map[key]; ConstructorInfo ctor = _t.GetConstructor(Type.EmptyTypes); if(ctor != null) { return (V) ctor.Invoke(null); } else throw new MenuItemNotFoundException(); } else throw new MenuItemNotFoundException(); } } #endregion #region OddEvenSplitters public interface IOddEvenSplitter { public (int, int) Split(IEnumerable data); } // these are the different implementation strategies // if you come up with your own, just add a new class and // make it implement IOddEvenSplitter public class OELinqSplitter : IOddEvenSplitter { public (int, int) Split(IEnumerable data) { int evens = (from n in data where n % 2 == 0 select n).Count(); return (evens, data.Count() - evens); } } public class OESequentialRunDoubleCountSplitter : IOddEvenSplitter { public (int, int) Split(IEnumerable src) { int odds = 0; int evens = 0; foreach(int n in src) { if(n % 2 == 0) evens++; else odds++; } return (evens, odds); } } public class OESequentialRunSingleCountSplitter : IOddEvenSplitter { public (int, int) Split(IEnumerable data) { int evens = 0; foreach(int n in data) { if(n % 2 == 0) evens++; } return (evens, data.Count() - evens); } } public class OESequentialRunDiffSplitter : IOddEvenSplitter { public (int, int) Split(IEnumerable data) { int diff = 0; foreach(int n in data) { diff += 1 - 2 * (n % 2); } return ((data.Count() + diff) / 2, (data.Count() - diff) / 2); } } #endregion } // end namespace Library // main program, using the library class Program { static Menu InitApp(Menu menu) { // register your commands here ! menu.Register("linq", typeof(OELinqSplitter)); menu.Register("dblcount", typeof(OESequentialRunDoubleCountSplitter)); menu.Register("sglcount", typeof(OESequentialRunSingleCountSplitter)); menu.Register("diff", typeof(OESequentialRunDiffSplitter)); return menu; } static void Main(string[] args) { // init the app Menu menu = InitApp(new Menu()); int[] data = { 1, 2, 3, 4, 5 }; // get input string command = Console.ReadLine(); // invoke strategy for the command try { var splitter = menu.GetInstanceAs(command); (int evens, int odds) = splitter.Split(data); Console.WriteLine($"Strategy: {splitter.GetType().Name}"); Console.WriteLine($"There are {evens} even numbers, and {odds} odd ones."); } catch(MenuItemNotFoundException ex) { Console.WriteLine($"Sorry, menu item '{command}' is not available."); } catch(Exception ex) { Console.WriteLine("Something went seriously wrong. Please contact the developer!"); } } } }

Odd-Even Splitters