Data commit

Task/Lah-numbers/C-sharp/lah-numbers.cs

@@ -0,0 +1,44 @@
+using System;
+using System.Linq;
+using System.Numerics;
+
+namespace LahNumbers {
+    class Program {
+        static BigInteger Factorial(BigInteger n) {
+            if (n == 0) return 1;
+            BigInteger res = 1;
+            while (n > 0) {
+                res *= n--;
+            }
+            return res;
+        }
+
+        static BigInteger Lah(BigInteger n, BigInteger k) {
+            if (k == 1) return Factorial(n);
+            if (k == n) return 1;
+            if (k > n) return 0;
+            if (k < 1 || n < 1) return 0;
+            return (Factorial(n) * Factorial(n - 1)) / (Factorial(k) * Factorial(k - 1)) / Factorial(n - k);
+        }
+
+        static void Main() {
+            Console.WriteLine("Unsigned Lah numbers: L(n, k):");
+            Console.Write("n/k ");
+            foreach (var i in Enumerable.Range(0, 13)) {
+                Console.Write("{0,10} ", i);
+            }
+            Console.WriteLine();
+            foreach (var row in Enumerable.Range(0, 13)) {
+                Console.Write("{0,-3}", row);
+                foreach (var i in Enumerable.Range(0, row + 1)) {
+                    var l = Lah(row, i);
+                    Console.Write("{0,11}", l);
+                }
+                Console.WriteLine();
+            }
+            Console.WriteLine("\nMaximum value from the L(100, *) row:");
+            var maxVal = Enumerable.Range(0, 100).Select(a => Lah(100, a)).Max();
+            Console.WriteLine(maxVal);
+        }
+    }
+}