Complete game

34_Digits/csharp/Guesser.cs

@@ -0,0 +1,52 @@
+namespace Digits;
+
+internal class Guesser
+{
+    private readonly IReadOnlyList<int> _weights = new List<int> { 0, 1, 3 }.AsReadOnly();
+    private readonly int[][,] _matrices = new[] { new int[3, 3], new int[9, 3], new int[27, 3] };
+    private readonly int[] _indices = new[] { 2, 8, 26 };
+    private readonly IRandom _random;
+
+    public Guesser(IRandom random)
+    {
+        _random = random;
+
+        for (int j = 0; j < 3; j++)
+        {
+            for (int i = 0; i < 3; i++) { _matrices[0][i, j] = 9; }
+            for (int i = 0; i < 9; i++) { _matrices[1][i, j] = i == 4 * j ? 2 : 3; }
+            for (int i = 0; i < 27; i++) { _matrices[2][i, j] = 1; }
+        }
+    }
+
+    public int GuessNextDigit()
+    {
+        var currentSum = 0;
+        var guess = 0;
+
+        for (int j = 0; j < 3; j++)
+        {
+            var sum = Enumerable.Range(0, 3).Aggregate((s, i) => s + GetWeightedValue(i, j));
+            if (sum > currentSum || _random.NextFloat() >= 0.5)
+            {
+                currentSum = sum;
+                guess = j;
+            }
+        }
+
+        return guess;
+    }
+
+    public void ObserveActualDigit(int digit)
+    {
+        for (int i = 0; i < 3; i++)
+        {
+            _matrices[i][_indices[i], digit]++;
+        }
+        _indices[2] = _indices[2] % 9 * 3 + digit;
+        _indices[1] = _indices[2] % 9;
+        _indices[0] = digit;
+    }
+
+    private int GetWeightedValue(int matrix, int row) => _weights[matrix] * _matrices[matrix][_indices[matrix], row];
+}