Zigzag

Program.cs

internal class Program
{
    private static void Main()
    {
        var head = new Node();
        CreateTree(head, 4, 2);
        head.Print(string.Empty, true);

        Console.WriteLine("Zigzag:");
        var zig = new Stack<Node>();
        var zag = new Stack<Node>();
        var reverse = false;
        
        zig.Push(head);
        while (zig.Count > 0)
        {
            while (zig.Count > 0)
            {
                var node = zig.Pop();
                foreach (var child in reverse ? node.Children.Reverse() : node.Children)
                {
                    zag.Push(child);
                }
                Console.Write(node.Value + " ");
            }

            Console.WriteLine();

            reverse = !reverse;

            var temp = zig;
            zig = zag;
            zag = temp;
        }
    }

    static void CreateTree(Node parent, int level, int count)
    {
        if (level == 0) return;

        parent.Children = Enumerable.Repeat(-1, count).Select(_ => new Node()).ToArray();

        foreach (var child in parent.Children)
        {
            CreateTree(child, level - 1, count);
        }
    }

    class Node
    {
        private static int _index = 1;

        public int Value { get; private set; }
        public Node[] Children { get; set; }

        public Node()
        {
            Value = _index;
            _index++;
            Children = new Node[0];
        }

        public void Print(string indent, bool last)
        {
            Console.Write(indent);
            if (last)
            {
                Console.Write("\\-");
                indent += "  ";
            }
            else
            {
                Console.Write("|-");
                indent += "| ";
            }
            Console.WriteLine(Value);

            for (var i = 0; i < Children.Length; i++)
                Children[i].Print(indent, i == Children.Length - 1);
        }
    }
}