Initial data commit

Task/Hailstone-sequence/C-sharp/hailstone-sequence-2.cs

@@ -0,0 +1,42 @@
+using System;
+using System.Collections.Generic;
+
+namespace ConsoleApplication1
+{
+    class Program
+    {
+        public static void Main()
+        {
+            int longestChain = 0, longestNumber = 0;
+
+            var recursiveLengths = new Dictionary<int, int>();
+
+            const int maxNumber = 100000;
+
+            for (var i = 1; i <= maxNumber; i++)
+            {
+                var chainLength = Hailstone(i, recursiveLengths);
+                if (longestChain >= chainLength)
+                    continue;
+
+                longestChain = chainLength;
+                longestNumber = i;
+            }
+            Console.WriteLine("max below {0}: {1} ({2} steps)", maxNumber, longestNumber, longestChain);
+        }
+
+        private static int Hailstone(int num, Dictionary<int, int> lengths)
+        {
+            if (num == 1)
+                return 1;
+
+            while (true)
+            {
+                if (lengths.ContainsKey(num))
+                    return lengths[num];
+
+                lengths[num] = 1 + ((num%2 == 0) ? Hailstone(num/2, lengths) : Hailstone((3*num) + 1, lengths));
+            }
+        }
+    }
+}