View difference between Paste ID: f5616ddda and

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+using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Diagnostics;
 
 namespace CSharp
 {
 	class Program
 	{
 		static Dictionary<uint, bool?> happyNumbers = new Dictionary<uint, bool?> { {1, true} };
 
 		static void Main (string [] args)
 		{
 			while (true) {
 				happyNumbers.Clear ();
 				Console.Write ("Pick an upper bound: ");
 				var input = Console.ReadLine ();
 				if (string.IsNullOrEmpty (input)) break;
 				var upperBound = uint.Parse (input);
 				var stopWatch = new Stopwatch ();
 				stopWatch.Start ();
 				var happies = HappyNumbers (upperBound);
 				stopWatch.Stop ();
 				Console.WriteLine ("Time taken to calculate numbers: {0}", stopWatch.Elapsed);
 				Console.WriteLine ("{0} happy number(s) between 0 and {1}.", happies.Count (), upperBound);
 				// I know this is slow, but I'm not timing the generation of the string
 				Console.Write ("Do you want the list? (Y/N)");
 				var list = Console.ReadLine ();
 				if (list.ToUpper ().Equals ("Y")) {
 					var numberList = string.Join (",", happies.Select (num => num.ToString ()).ToArray ());
 					Console.WriteLine ("Number list: {0}", numberList);
 				}
 			}
 		}
 
 		static IEnumerable<uint> HappyNumbers (uint upperBound) {
 			var numbers = new List<uint> { 1 };
 			for (uint current = 2; current < upperBound; ++current) {
 				var happiness = IsHappy (current);
 				if (happiness.HasValue && happiness.Value) numbers.Add (current);
 			}
 			return numbers;
 		}
 
 		static bool? IsHappy (uint value)
 		{
 			bool? happiness;
 
 			if (happyNumbers.TryGetValue (value, out happiness)) {
 				if (happiness == null) return happyNumbers[value] = false;
 			} else {
 				happyNumbers[value] = happiness = null;
 				uint newValue = 0;
 
 				for (uint i = value; i != 0; i /= 10) {
 					uint lsd = i % 10;
 					newValue += lsd * lsd;
 				}
 
 				if (newValue == 1) happiness = true;
 				else happiness = IsHappy (newValue);
 
 				if (happiness.HasValue && happiness.Value) happyNumbers[value] = true;
 				else happyNumbers[value] = happiness;
 			}
 
 			return happiness;
 		}
 	}
 }