Data commit

Task/Vampire-number/C-sharp/vampire-number.cs

@@ -0,0 +1,90 @@
+using System;
+
+namespace RosettaVampireNumber
+{
+    class Program
+    {
+        static void Main(string[] args)
+        {
+            int i, j, n;
+            ulong x;
+            var f = new ulong[16];
+            var bigs = new ulong[] { 16758243290880UL, 24959017348650UL, 14593825548650UL, 0 };
+            ulong[] tens = new ulong[20];
+            tens[0] = 1;
+            for (i = 1; i < 20; i++)
+                tens[i] = tens[i - 1] * 10;
+
+            for (x = 1, n = 0; n < 25; x++)
+            {
+                if ((j = fangs(x, f, tens)) == 0) continue;
+                Console.Write(++n + ": ");
+                show_fangs(x, f, j);
+            }
+
+            Console.WriteLine();
+            for (i = 0; bigs[i] > 0 ; i++)
+            {
+                if ((j = fangs(bigs[i], f, tens)) > 0)
+                    show_fangs(bigs[i], f, j);
+                else
+                    Console.WriteLine(bigs[i] + " is not vampiric.");
+            }
+            Console.ReadLine();
+        }
+
+        private static void show_fangs(ulong x, ulong[] f, int cnt)
+        {
+            Console.Write(x);
+            int i;
+            for (i = 0; i < cnt; i++)
+                Console.Write(" = " + f[i] + " * " + (x / f[i]));
+            Console.WriteLine();
+        }
+
+        private static int fangs(ulong x, ulong[] f, ulong[] tens)
+        {
+            int n = 0;
+            int nd = ndigits(x);
+            if ((nd & 1) > 0) return 0;
+            nd /= 2;
+
+            ulong lo, hi;
+            lo = Math.Max(tens[nd - 1], (x + tens[nd] - 2) / (tens[nd] - 1));
+            hi = Math.Min(x / lo, (ulong) Math.Sqrt(x));
+
+            ulong a, b, t = dtally(x);
+            for (a = lo; a <= hi; a++)
+            {
+                b = x / a;
+                if (a * b == x && ((a % 10) > 0 || (b % 10) > 0) && t == dtally(a) + dtally(b))
+                    f[n++] = a;
+            }
+
+            return n;
+        }
+
+        private static ulong dtally(ulong x)
+        {
+            ulong t = 0;
+            while (x > 0)
+            {
+                t += 1UL << (int)((x % 10) * 6);
+                x /= 10;
+            }
+
+            return t;
+        }
+
+        private static int ndigits(ulong x)
+        {
+            int n = 0;
+            while (x > 0)
+            {
+                n++;
+                x /= 10;
+            }
+            return n;
+        }
+    }
+}