Hanoi.cs

using System;
using System.Collections.Generic;
using System.Linq;

namespace Hanoi {
	class HanoiTower {
		static void Main(string[] args) {
			int height;
			if (args.Length == 0 || !int.TryParse(args[0], out height)) height = 3;
			var count = 0;
			foreach (var towers in new HanoiTower(height).Resolve()) Console.WriteLine("\n=== STEP: {0} ===\n{1}", ++count, towers.Select(i => i.Reverse().Aggregate("|", (l, r) => l + r + "|")).Aggregate((l, r) => l + "\n" + r));
		}

		private readonly Stack<int> sourceTower = new Stack<int>();
		private readonly Stack<int> bareTower = new Stack<int>();
		private readonly Stack<int> destinationTower = new Stack<int>();

		public HanoiTower(int height) => Enumerable.Range(0, height).Select(i => height - i).ToList().ForEach(sourceTower.Push);

		private IEnumerable<Stack<int>[]> Resolve() => Resolve(sourceTower.Count(), sourceTower, bareTower, destinationTower);

		private IEnumerable<Stack<int>[]> Resolve(int height, params Stack<int>[] towers) {
			if (height > 1) foreach (var ret in Resolve(height - 1, towers[0], towers[2], towers[1])) yield return ret;
			towers[2].Push(towers[0].Pop());
			yield return new[] { sourceTower, bareTower, destinationTower };
			if (height > 1) foreach (var ret in Resolve(height - 1, towers[1], towers[0], towers[2])) yield return ret;
		}
	}
}