Satisfactory check

SudoScript.Core.Test/SolverTests.cs

@@ -6,17 +6,7 @@ namespace SudoScript.Core.Test;
 
 internal sealed class SolverTests
 {
-    [Test()]
-    public void CanSolveEmptySudoku()
-    {
-        Board board = Util.CreateStandardEmpty();
-        Assert.DoesNotThrow(() => board = Solver.Solve(board));
-        Assert.IsTrue(board.ValidateRules());
-        Assert.IsFalse(board.Cells().Any(c => c.Digit == Cell.EmptyDigit));
-    }
-
-    [Test]
-    public void CanSolveGeneratedSudoku()
+    public Board CreateEasyBoard()
     {
         Board board = Util.CreateStandardEmpty();
         // Sudoku givens generated by https://sudoku.com/
@@ -39,6 +29,7 @@ public void CanSolveGeneratedSudoku()
         board[8, 4].Digit = 8;
 
         board[3, 5].Digit = 4;
+        board[4, 7].Digit = 2;
 
         board[3, 6].Digit = 6;
         board[5, 6].Digit = 7;
@@ -50,6 +41,7 @@ public void CanSolveGeneratedSudoku()
         board[8, 7].Digit = 3;
         board[9, 7].Digit = 5;
 
+        board[3, 9].Digit = 1;
         board[2, 8].Digit = 9;
         board[4, 8].Digit = 7;
         board[5, 8].Digit = 4;
@@ -59,6 +51,23 @@ public void CanSolveGeneratedSudoku()
         board[7, 9].Digit = 9;
         board[8, 9].Digit = 7;
 
+        return board;
+    }
+
+    [Test()]
+    public void CanSolveEmptySudoku()
+    {
+        Board board = Util.CreateStandardEmpty();
+        Assert.DoesNotThrow(() => board = Solver.Solve(board));
+        Assert.IsTrue(board.ValidateRules());
+        Assert.IsFalse(board.Cells().Any(c => c.Digit == Cell.EmptyDigit));
+    }
+
+    [Test]
+    public void CanSolveGeneratedSudoku()
+    {
+        Board board = CreateEasyBoard();
+
         Console.WriteLine(board.ToString());
 
         Console.WriteLine("-------------------------------------------------");
@@ -68,4 +77,21 @@ public void CanSolveGeneratedSudoku()
 
         Console.WriteLine(board.ToString());
     }
+
+    [Test]
+    public void IsSatisfactoryTest()
+    {
+        Board board = CreateEasyBoard();
+
+        Assert.IsTrue(Solver.IsSatisfactory(board));
+    }
+
+    [Test]
+    public void IsNotSatisfactoryTest()
+    {
+        Board board = Util.CreateStandardEmpty();
+
+        Assert.IsFalse(Solver.IsSatisfactory(board));
+    }
+
 }

SudoScript.Core/Solver.cs

@@ -20,7 +20,7 @@ public static Board Solve(Board board)
 
     private static bool SolveRec(Board board, [NotNullWhen(true)] out Board? solvedBoard)
     {
-        // Eliminate candidates from all rules untill nothing changes.
+        // Eliminate candidates from all rules until nothing changes.
         while (board.EliminateCandidates()) ;
 
         // We hit an invalid state, and must backtrack.
@@ -42,14 +42,14 @@ private static bool SolveRec(Board board, [NotNullWhen(true)] out Board? solvedB
         orderedCells = orderedCells.SkipWhile(c => c.CandidateCount <= 1);
         // The first cell contains the smallest amount of candidates.
         int lowestCandidateCount = orderedCells.FirstOrDefault()?.CandidateCount ?? 1;
-        // Take all cells with the least amount of candidates.
-        orderedCells = orderedCells.TakeWhile(c => c.CandidateCount == lowestCandidateCount);
         // If there are no cells with more than 1 candidate, the board is solved.
         if (lowestCandidateCount == 1)
         {
             solvedBoard = board;
             return true;
         }
+        // Take all cells with the least amount of candidates.
+        orderedCells = orderedCells.TakeWhile(c => c.CandidateCount == lowestCandidateCount);
 
         Cell cell = orderedCells.First();
         foreach (int candidate in cell.Candidates())
@@ -76,9 +76,17 @@ public static Board GenerateSolveable(Board board)
         throw new NotImplementedException();
     }
 
-    public static bool IsSatisfactory(Board board)
+    /// <summary>
+    /// Checks if the board can be solved by just using the EliminateCandidates methods from units.
+    /// </summary>
+    /// <param name="board"></param>
+    /// <returns>True if the board can be solved without trial and error guessing.</returns>
+    public static bool IsSatisfactory(Board board) // Certain methods for eliminating candidates using inference are not currently implemented. Implementing them would make this function more acurate.
     {
-        throw new NotImplementedException();
+        // Eliminate candidates from all rules untill nothing changes.
+        while (board.EliminateCandidates());
+        // If the board is solved, it does not require trial and error.
+        return board.IsSolved();
     }
 
     public static bool IsProper(Board board)