added NextNumberChooser

uqac-ia-sudoku-csp/Interfaces/INextNumberChooser.cs

+using System.Collections.Generic;
+
+namespace uqac_ia_sudoku_csp.Interfaces
+{
+    public interface INextNumberChooser
+    {
+        IEnumerable<int> ChooseNext(Board board, int x, int y);
+    }
+}

uqac-ia-sudoku-csp/Program.cs

 using uqac_ia_sudoku_csp.Interfaces;
 using uqac_ia_sudoku_csp.Solver;
 using uqac_ia_sudoku_csp.Solver.Generators;
+using uqac_ia_sudoku_csp.Solver.NextNumberChoosers;
 using uqac_ia_sudoku_csp.Solver.NextValueChoosers;
 
 namespace uqac_ia_sudoku_csp
             {
                 valueChooser = args[1];
             }
-            var emptyCharacters = "0 .";
+            var numberChooser = "basic";
             if (args.Length > 2)
             {
-                emptyCharacters = args[2];
+                numberChooser = args[2];
+            }
+            var emptyCharacters = "0 .";
+            if (args.Length > 3)
+            {
+                emptyCharacters = args[3];
             }
 
             object data;
                 Environment.Exit(64);
             }
 
-            var solver = new BacktrackSearch(nextCellChooser);
+            INextNumberChooser nextNumberChooser = null;
+            if (numberChooser == "basic")
+            {
+                nextNumberChooser = new BasicNextNumberChooser();
+            }
+            else
+            {
+                Console.Error.WriteLine("Invalid next number chooser");
+                Environment.Exit(64);
+            }
+
+            var solver = new BacktrackSearch(nextCellChooser, nextNumberChooser);
             var resolved = solver.Resolve(board);
 
             if (resolved.Success)

uqac-ia-sudoku-csp/Solver/BacktrackSearch.cs

 using System;
 using System.Collections.Generic;
-using System.Linq;
 using uqac_ia_sudoku_csp.Interfaces;
 using uqac_ia_sudoku_csp.Solver.Constraints;
 
     public class BacktrackSearch : ISolver
     {
         private readonly INextCellChooser _nextCellChooser;
+        private readonly INextNumberChooser _nextNumberChooser;
         protected IList<IConstraint> Constraints;
 
-        public BacktrackSearch(INextCellChooser nextCellChooser)
+        public BacktrackSearch(INextCellChooser nextCellChooser, INextNumberChooser nextNumberChooser)
         {
             _nextCellChooser = nextCellChooser;
+            _nextNumberChooser = nextNumberChooser;
             Constraints = new List<IConstraint>
             {
                 new LineContraint(),
 
         public SolverResult Resolve(Board board)
         {
-            var domain = Enumerable.Range(0, board.Size).ToList();
             var result = new SolverResult();
             var start = DateTime.Now;
-            result.Success = RecursiveResolve(board, result, domain);
+            result.Success = RecursiveResolve(board, result);
             var end = DateTime.Now;
             result.Elapsed = end - start;
             return result;
         }
 
-        protected bool RecursiveResolve(Board board, SolverResult result, IList<int> domain)
+        protected bool RecursiveResolve(Board board, SolverResult result)
         {
             if (board.IsComplete())
             {
             _nextCellChooser.SelectVariable(board, out x, out y, Constraints);
             if (x != -1 && y != -1)
             {
-                foreach (var value in domain)
+                foreach (var value in _nextNumberChooser.ChooseNext(board, x, y))
                 {
                     ++result.TryCount;
                     board.SetNumber(x, y, value);
                     if (board.IsConsistent(x, y, Constraints))
                     {
                         ++result.ConsistentTryCount;
-                        if (RecursiveResolve(board, result, domain))
+                        if (RecursiveResolve(board, result))
                         {
                             return true;
                         }

uqac-ia-sudoku-csp/Solver/NextNumberChoosers/BasicNextNumberChooser.cs

+using System.Collections.Generic;
+using System.Linq;
+using uqac_ia_sudoku_csp.Interfaces;
+
+namespace uqac_ia_sudoku_csp.Solver.NextNumberChoosers
+{
+    public class BasicNextNumberChooser : INextNumberChooser
+    {
+        public IEnumerable<int> ChooseNext(Board board, int x, int y)
+        {
+            return Enumerable.Range(0, board.Size);
+        }
+    }
+}