2016 Update

Task/Dinesmans-multiple-dwelling-problem/C-sharp/dinesmans-multiple-dwelling-problem.cs

@@ -0,0 +1,68 @@
+public class Program
+{
+    public static void Main()
+    {
+        const int count = 5;
+        const int Baker = 0, Cooper = 1, Fletcher = 2, Miller = 3, Smith = 4;
+        string[] names = { nameof(Baker), nameof(Cooper), nameof(Fletcher), nameof(Miller), nameof(Smith) };
+
+        Func<int[], bool>[] constraints = {
+            floorOf => floorOf[Baker] != count-1,
+            floorOf => floorOf[Cooper] != 0,
+            floorOf => floorOf[Fletcher] != count-1 && floorOf[Fletcher] != 0,
+            floorOf => floorOf[Miller] > floorOf[Cooper],
+            floorOf => Math.Abs(floorOf[Smith] - floorOf[Fletcher]) > 1,
+            floorOf => Math.Abs(floorOf[Fletcher] - floorOf[Cooper]) > 1,
+        };
+
+        var solver = new DinesmanSolver();
+        foreach (var tenants in solver.Solve(count, constraints)) {
+            Console.WriteLine(string.Join(" ", tenants.Select(t => names[t])));
+        }
+    }
+}
+
+public class DinesmanSolver
+{
+    public IEnumerable<int[]> Solve(int count, params Func<int[], bool>[] constraints) {
+        foreach (int[] floorOf in Permutations(count)) {
+            if (constraints.All(c => c(floorOf))) {
+                yield return Enumerable.Range(0, count).OrderBy(i => floorOf[i]).ToArray();
+            }
+        }
+    }
+
+    static IEnumerable<int[]> Permutations(int length) {
+        if (length == 0) {
+            yield return new int[0];
+            yield break;
+        }
+        bool forwards = false;
+        foreach (var permutation in Permutations(length - 1)) {
+            for (int i = 0; i < length; i++) {
+                yield return permutation.InsertAt(forwards ? i : length - i - 1, length - 1).ToArray();
+            }
+            forwards = !forwards;
+        }
+    }
+}
+
+static class Extensions
+{
+    public static IEnumerable<T> InsertAt<T>(this IEnumerable<T> source, int position, T newElement) {
+        if (source == null) throw new ArgumentNullException(nameof(source));
+        if (position < 0) throw new ArgumentOutOfRangeException(nameof(position));
+        return InsertAtIterator(source, position, newElement);
+    }
+
+    private static IEnumerable<T> InsertAtIterator<T>(IEnumerable<T> source, int position, T newElement) {
+        int index = 0;
+        foreach (T element in source) {
+            if (index == position) yield return newElement;
+            yield return element;
+            index++;
+        }
+        if (index < position) throw new ArgumentOutOfRangeException(nameof(position));
+        if (index == position) yield return newElement;
+    }
+}