three jugs problem with DFS

using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        var moves = Poisson(new[] { 3, 5, 8 }, new[] { 0, 0, 8 }, 4);
        if (moves == null)
            Console.WriteLine("No solution!");
        else
            foreach (var move in moves)
                Console.WriteLine("{0} --> {1}, quantity: {2}", move.Item1, move.Item2, move.Item3);
    }

    static List<Tuple<int, int, int>> Poisson(
        int[] max,
        int[] now,
        int goal, // d
        List<Tuple<int, int, int>> moves = null,
        HashSet<Tuple<int, int, int>> seen = null)
    {

        moves = moves ?? new List<Tuple<int, int, int>>();
        seen = seen ?? new HashSet<Tuple<int, int, int>>();

        // been here before?
        if (!seen.Add(Tuple.Create(now[0], now[1], now[2])))
            return null;

        // check for success
        for (int ii = 0; ii < now.Length; ++ii)
            if (now[ii] == goal)
                return moves;

        for (int from = 0; from < now.Length; ++from)
            for (int to = 0; to < now.Length; ++to)
            {

                if (from == to || now[from] == 0 || now[to] == max[to])
                    continue;

                int qty = Math.Min(max[to] - now[to], now[from]);

                // pour from --> to

                now[to] += qty;
                now[from] -= qty;

                moves.Add(Tuple.Create(from, to, qty));
                if (Poisson(max, now, goal, moves, seen) != null)
                    return moves;

                // revert move
                now[from] += qty;
                now[to] -= qty;
                moves.RemoveAt(moves.Count - 1);
            }

        // failed
        return null;
    }

}