Add computer strategy

72_Queen/csharp/Game.cs

@@ -0,0 +1,164 @@
+namespace Queen;
+
+internal class Game
+{
+    private readonly IReadWrite _io;
+    private readonly IRandom _random;
+    private readonly Computer _computer;
+
+    public Game(IReadWrite io, IRandom random)
+    {
+        _io = io;
+        _random = random;
+        _computer = new Computer(random);
+    }
+
+    internal void PlaySeries()
+    {
+        _io.Write(Streams.Title);
+        if (_io.ReadYesNo(Prompts.Instructions)) { _io.Write(Streams.Instructions); }
+
+        while (true)
+        {
+            var result = PlayGame();
+            _io.Write(result switch
+            {
+                Result.HumanForfeits => Streams.Forfeit,
+                Result.HumanWins => Streams.Congratulations,
+                Result.ComputerWins => Streams.IWin,
+                _ => throw new InvalidOperationException($"Unexpected result {result}")
+            });
+
+            if (!_io.ReadYesNo(Prompts.Anyone)) { break; }
+        }
+
+        _io.Write(Streams.Thanks);
+    }
+
+    private Result PlayGame()
+    {
+        _io.Write(Streams.Board);
+        var humanPosition = _io.ReadPosition(Prompts.Start, p => p.IsStart, Streams.IllegalStart, repeatPrompt: true);
+        if (humanPosition.IsZero) { return Result.HumanForfeits; }
+
+        while (true)
+        {
+            var computerPosition = _computer.GetMove(humanPosition);
+            if (computerPosition.IsEnd) { return Result.ComputerWins; }
+        }
+
+    }
+
+    private enum Result { ComputerWins, HumanWins, HumanForfeits };
+}
+
+internal class Computer
+{
+    private static readonly HashSet<Position> _randomiseFrom = new() { 41, 44, 73, 75, 126, 127 };
+    private static readonly HashSet<Position> _desirable = new() { 73, 75, 126, 127, 158 };
+    private readonly IRandom _random;
+
+    public Computer(IRandom random)
+    {
+        _random = random;
+    }
+
+    public Position GetMove(Position from)
+        => from + (_randomiseFrom.Contains(from) ? _random.NextMove() : FindMove(from));
+
+    private Move FindMove(Position from)
+    {
+        for (int i = 7; i > 0; i--)
+        {
+            if (IsOptimal(Move.Left, out var move)) { return move; }
+            if (IsOptimal(Move.Down, out move)) { return move; }
+            if (IsOptimal(Move.DownLeft, out move)) { return move; }
+
+            bool IsOptimal(Move direction, out Move move)
+            {
+                move = direction * i;
+                return _desirable.Contains(from + move);
+            }
+        }
+
+        return _random.NextMove();
+    }
+}
+
+internal static class IOExtensions
+{
+    internal static bool ReadYesNo(this IReadWrite io, string prompt)
+    {
+        while (true)
+        {
+            var answer = io.ReadString(prompt).ToLower();
+            if (answer == "yes") { return true; }
+            if (answer == "no") { return false; }
+
+            io.Write(Streams.YesOrNo);
+        }
+    }
+
+    internal static Position ReadPosition(
+        this IReadWrite io,
+        string prompt,
+        Predicate<Position> isValid,
+        Stream error,
+        bool repeatPrompt = false)
+    {
+        while (true)
+        {
+            var response = io.ReadNumber(prompt);
+            var number = (int)response;
+            var position = new Position(number);
+            if (number == response && (position.IsZero || isValid(position)))
+            {
+                return position;
+            }
+
+            io.Write(error);
+            if (!repeatPrompt) { prompt = ""; }
+        }
+    }
+}
+
+internal record struct Position(int Diagonal, int Row)
+{
+    public static readonly Position Zero = new(0);
+
+    public Position(int number)
+        : this(Diagonal: number / 10, Row: number % 10)
+    {
+    }
+
+    public bool IsZero => Row == 0 && Diagonal == 0;
+    public bool IsStart => Row == 1 || Row == Diagonal;
+    public bool IsEnd => Row == 8 && Diagonal == 15;
+
+    public override string ToString() => $"{Diagonal}{Row}";
+
+    public static implicit operator Position(int value) => new(value);
+
+    public static Position operator +(Position position, Move move)
+        => new(Diagonal: position.Diagonal + move.Diagonal, Row: position.Row + move.Row);
+}
+
+internal static class RandomExtensions
+{
+    internal static Move NextMove(this IRandom random)
+        => random.NextFloat() switch
+        {
+            > 0.6F => Move.Down,
+            > 0.3F => Move.DownLeft,
+            _ => Move.Left
+        };
+}
+
+internal record struct Move(int Diagonal, int Row)
+{
+    public static readonly Move Left = new(1, 0);
+    public static readonly Move DownLeft = new(2, 1);
+    public static readonly Move Down = new(1, 1);
+
+    public static Move operator *(Move move, int scale) => new(move.Diagonal * scale, move.Row * scale);
+}

72_Queen/csharp/Games.cs

@@ -1,96 +0,0 @@
-namespace Queen;
-
-internal class Games
-{
-    private readonly IReadWrite _io;
-    private readonly IRandom _random;
-
-    public Games(IReadWrite io, IRandom random)
-    {
-        _io = io;
-        _random = random;
-    }
-
-    internal void Play()
-    {
-        _io.Write(Streams.Title);
-        if (_io.ReadYesNo(Prompts.Instructions)) { _io.Write(Streams.Instructions); }
-
-        while (true)
-        {
-            PlayGame();
-
-            if (!_io.ReadYesNo(Prompts.Anyone))
-            {
-                _io.Write(Streams.Thanks);
-                return;
-            }
-        }
-    }
-
-    internal void PlayGame()
-    {
-        _io.Write(Streams.Board);
-        var humanPosition = _io.ReadPosition(Prompts.Start, p => p.IsStart, Streams.IllegalStart, repeatPrompt: true)
-        if (humanPosition.IsZero)
-        {
-            _io.Write(Streams.Forfeit);
-            return;
-        }
-
-
-    }
-}
-
-internal static class IOExtensions
-{
-    internal static bool ReadYesNo(this IReadWrite io, string prompt)
-    {
-        while (true)
-        {
-            var answer = io.ReadString(prompt).ToLower();
-            if (answer == "yes") { return true; }
-            if (answer == "no") { return false; }
-
-            io.Write(Streams.YesOrNo);
-        }
-    }
-
-    internal static Position ReadPosition(
-        this IReadWrite io,
-        string prompt,
-        Predicate<Position> isValid,
-        Stream error,
-        bool repeatPrompt = false)
-    {
-        while (true)
-        {
-            var response = io.ReadNumber(prompt);
-            var number = (int)response;
-            var position = new Position(number);
-            if (number == response && (position.IsZero || isValid(position)))
-            {
-                return position;
-            }
-
-            io.Write(error);
-            if (!repeatPrompt) { prompt = ""; }
-        }
-    }
-}
-
-internal record struct Position(int Diagonal, int Row)
-{
-    public static readonly Position Zero = new(0);
-
-    public Position(int number)
-        : this(Diagonal: number / 10, Row: number % 10)
-    {
-    }
-
-    public bool IsZero => Row == 0 && Diagonal == 0;
-    public bool IsStart => Row == 1 || Row == Diagonal;
-    public bool IsEnd => Row == 8 && Diagonal == 15;
-
-    public override string ToString() => $"{Diagonal}{Row}";
-}

72_Queen/csharp/Program.cs

@@ -4,4 +4,4 @@ global using static Queen.Resources.Resource;
 
 using Queen;
 
-new Games(new ConsoleIO(), new RandomNumberGenerator()).Play();
+new Game(new ConsoleIO(), new RandomNumberGenerator()).PlaySeries();

72_Queen/csharp/Resources/Board.txt

@@ -1,4 +1,5 @@
 
+ 
  81  71  61  51  41  31  21  11
 
 

72_Queen/csharp/Resources/Forfeit.txt

@@ -1,2 +1,3 @@
-Looks like I have won by forfeit.
+
+It looks like I have won by forfeit.
 

72_Queen/csharp/Resources/Instructions.txt

@@ -13,4 +13,3 @@ We alternate moves.
 You may forfeit by typing '0' as your move.
 Be sure to press the return key after each response.
 
-

72_Queen/csharp/Resources/Thanks.txt

@@ -1 +1,3 @@
+
+
 Ok --- thanks again.