Simplify Mastermind (C#) folder structure

60_Mastermind/csharp/Code.cs

@@ -0,0 +1,91 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace Game
+{
+    /// <summary>
+    /// Represents a secret code in the game.
+    /// </summary>
+    public class Code
+    {
+        private readonly int[] m_colors;
+
+        /// <summary>
+        /// Initializes a new instance of the Code class from the given set
+        /// of positions.
+        /// </summary>
+        /// <param name="colors">
+        /// Contains the color for each position.
+        /// </param>
+        public Code(IEnumerable<int> colors)
+        {
+            m_colors = colors.ToArray();
+            if (m_colors.Length == 0)
+                throw new ArgumentException("A code must contain at least one position");
+        }
+
+        /// <summary>
+        /// Compares this code with the given code.
+        /// </summary>
+        /// <param name="other">
+        /// The code to compare.
+        /// </param>
+        /// <returns>
+        /// A number of black pegs and a number of white pegs.  The number
+        /// of black pegs is the number of positions that contain the same
+        /// color in both codes.  The number of white pegs is the number of
+        /// colors that appear in both codes, but in the wrong positions.
+        /// </returns>
+        public (int blacks, int whites) Compare(Code other)
+        {
+            // What follows is the O(N^2) from the original BASIC program
+            // (where N is the number of positions in the code).  Note that
+            // there is an O(N) algorithm.  (Finding it is left as an
+            // exercise for the reader.)
+            if (other.m_colors.Length != m_colors.Length)
+                throw new ArgumentException("Only codes of the same length can be compared");
+
+            // Keeps track of which positions in the other code have already
+            // been marked as exact or close matches.
+            var consumed = new bool[m_colors.Length];
+
+            var blacks = 0;
+            var whites = 0;
+
+            for (var i = 0; i < m_colors.Length; ++i)
+            {
+                if (m_colors[i] == other.m_colors[i])
+                {
+                    ++blacks;
+                    consumed[i] = true;
+                }
+                else
+                {
+                    // Check if the current color appears elsewhere in the
+                    // other code.  We must be careful not to consider
+                    // positions that are also exact matches.
+                    for (var j = 0; j < m_colors.Length; ++j)
+                    {
+                        if (!consumed[j] &&
+                            m_colors[i] == other.m_colors[j] &&
+                            m_colors[j] != other.m_colors[j])
+                        {
+                            ++whites;
+                            consumed[j] = true;
+                            break;
+                        }
+                    }
+                }
+            }
+
+            return (blacks, whites);
+        }
+
+        /// <summary>
+        /// Gets a string representation of the code.
+        /// </summary>
+        public override string ToString() =>
+            new (m_colors.Select(index => Colors.List[index].ShortName).ToArray());
+    }
+}