Data commit

Task/Bell-numbers/C-sharp/bell-numbers.cs

@@ -0,0 +1,55 @@
+using System;
+using System.Numerics;
+
+namespace BellNumbers {
+    public static class Utility {
+        public static void Init<T>(this T[] array, T value) {
+            if (null == array) return;
+            for (int i = 0; i < array.Length; ++i) {
+                array[i] = value;
+            }
+        }
+    }
+
+    class Program {
+        static BigInteger[][] BellTriangle(int n) {
+            BigInteger[][] tri = new BigInteger[n][];
+            for (int i = 0; i < n; ++i) {
+                tri[i] = new BigInteger[i];
+                tri[i].Init(BigInteger.Zero);
+            }
+            tri[1][0] = 1;
+            for (int i = 2; i < n; ++i) {
+                tri[i][0] = tri[i - 1][i - 2];
+                for (int j = 1; j < i; ++j) {
+                    tri[i][j] = tri[i][j - 1] + tri[i - 1][j - 1];
+                }
+            }
+            return tri;
+        }
+
+        static void Main(string[] args) {
+            var bt = BellTriangle(51);
+            Console.WriteLine("First fifteen and fiftieth Bell numbers:");
+            for (int i = 1; i < 16; ++i) {
+                Console.WriteLine("{0,2}: {1}", i, bt[i][0]);
+            }
+            Console.WriteLine("50: {0}", bt[50][0]);
+            Console.WriteLine();
+            Console.WriteLine("The first ten rows of Bell's triangle:");
+            for (int i = 1; i < 11; ++i) {
+                //Console.WriteLine(bt[i]);
+                var it = bt[i].GetEnumerator();
+                Console.Write("[");
+                if (it.MoveNext()) {
+                    Console.Write(it.Current);
+                }
+                while (it.MoveNext()) {
+                    Console.Write(", ");
+                    Console.Write(it.Current);
+                }
+                Console.WriteLine("]");
+            }
+        }
+    }
+}