September 2017 Update

Task/Ackermann-function/C-sharp/ackermann-function.cs

@@ -1,32 +1,127 @@
 using System;
-class Program
+using System.Numerics;
+using System.IO;
+using System.Diagnostics;
+
+namespace Ackermann_Function
 {
-    public static long Ackermann(long m, long n)
+    class Program
     {
-        if(m > 0)
+        static void Main(string[] args)
         {
-            if (n > 0)
-                return Ackermann(m - 1, Ackermann(m, n - 1));
-            else if (n == 0)
-                return Ackermann(m - 1, 1);
-        }
-        else if(m == 0)
-        {
-            if(n >= 0)
-                return n + 1;
-        }
-
-        throw new System.ArgumentOutOfRangeException();
-    }
-
-    static void Main()
-    {
-        for (long m = 0; m <= 3; ++m)
-        {
-            for (long n = 0; n <= 4; ++n)
+            int _m = 0;
+            int _n = 0;
+            Console.Write("m = ");
+            try
             {
-                Console.WriteLine("Ackermann({0}, {1}) = {2}", m, n, Ackermann(m, n));
+                _m = Convert.ToInt32(Console.ReadLine());
             }
+            catch (Exception)
+            {
+                Console.WriteLine("Please enter a number.");
+            }
+            Console.Write("n = ");
+            try
+            {
+                _n = Convert.ToInt32(Console.ReadLine());
+            }
+            catch (Exception)
+            {
+                Console.WriteLine("Please enter a number.");
+            }
+            //for (long m = 0; m <= 10; ++m)
+            //{
+            //    for (long n = 0; n <= 10; ++n)
+            //    {
+            //        DateTime now = DateTime.Now;
+            //        Console.WriteLine("Ackermann({0}, {1}) = {2}", m, n, Ackermann(m, n));
+            //        Console.WriteLine("Time taken:{0}", DateTime.Now - now);
+            //    }
+            //}
+
+            DateTime now = DateTime.Now;
+            Console.WriteLine("Ackermann({0}, {1}) = {2}", _m, _n, Ackermann(_m, _n));
+            Console.WriteLine("Time taken:{0}", DateTime.Now - now);
+            File.WriteAllText("number.txt", Ackermann(_m, _n).ToString());
+            Process.Start("number.txt");
+            Console.ReadKey();
+        }
+        public class OverflowlessStack<T>
+        {
+            internal sealed class SinglyLinkedNode
+            {
+                private const int ArraySize = 2048;
+                T[] _array;
+                int _size;
+                public SinglyLinkedNode Next;
+                public SinglyLinkedNode()
+                {
+                    _array = new T[ArraySize];
+                }
+                public bool IsEmpty { get { return _size == 0; } }
+                public SinglyLinkedNode Push(T item)
+                {
+                    if (_size == ArraySize - 1)
+                    {
+                        SinglyLinkedNode n = new SinglyLinkedNode();
+                        n.Next = this;
+                        n.Push(item);
+                        return n;
+                    }
+                    _array[_size++] = item;
+                    return this;
+                }
+                public T Pop()
+                {
+                    return _array[--_size];
+                }
+            }
+            private SinglyLinkedNode _head = new SinglyLinkedNode();
+
+            public T Pop()
+            {
+                T ret = _head.Pop();
+                if (_head.IsEmpty && _head.Next != null)
+                    _head = _head.Next;
+                return ret;
+            }
+            public void Push(T item)
+            {
+                _head = _head.Push(item);
+            }
+            public bool IsEmpty
+            {
+                get { return _head.Next == null && _head.IsEmpty; }
+            }
+        }
+        public static BigInteger Ackermann(BigInteger m, BigInteger n)
+        {
+            var stack = new OverflowlessStack<BigInteger>();
+            stack.Push(m);
+            while (!stack.IsEmpty)
+            {
+                m = stack.Pop();
+            skipStack:
+                if (m == 0)
+                    n = n + 1;
+                else if (m == 1)
+                    n = n + 2;
+                else if (m == 2)
+                    n = n * 2 + 3;
+                else if (n == 0)
+                {
+                    --m;
+                    n = 1;
+                    goto skipStack;
+                }
+                else
+                {
+                    stack.Push(m - 1);
+                    --n;
+                    goto skipStack;
+                }
+            }
+            return n;
         }
     }
 }