Non Recursive Puzzle Solver

    public IEnumerator NonRecursiveTileIterator(int i)
    {
        ulong possibilities = (ulong)Mathf.Pow(2, width*height);
        bool skip_this_iteration;
        while (true)
        {
        currently_checking_for_solutions = true;
            skip_this_iteration = false;
            if (possibilities % 1000000 == 0) yield return null;
            for(int x = 0; x < currentState.Length; x++)
            {
                currentState[x] = ((possibilities & (ulong)(1<<x)) != 0);
                if(lockedTiles[x] && currentState[x] != startingState[x])
                {
                    skip_this_iteration = true;
                    break;
                }
            }
            if(!skip_this_iteration)
            {
                if(isSolved())
                {
                     SolutionList.Add(currentState.Clone());
                }
            }
            if(possibilities==0) yield break;
            possibilities--;
        }
    }