leetcode297

public class Codec
    {
        // Encodes a tree to a single string.
        public string serialize(TreeNode root)
        {
            if (root == null)
                return "";

            Queue<TreeNode> queue = new Queue<TreeNode>();
            StringBuilder result = new StringBuilder();

            queue.Enqueue(root);
            while (true)
            {
                if (queue.Count() == 0)
                    break;

                int nodesAtLevel = queue.Count();
                StringBuilder list = new StringBuilder();
                for (int i = 0; i < nodesAtLevel; i++)
                {
                    var node = queue.Dequeue();
                    if (node != null)
                    {
                        list.Append(node.val.ToString() + ",");
                        if (node.left != null)
                            queue.Enqueue(node.left);
                        else
                            queue.Enqueue(null);

                        if (node.right != null)
                            queue.Enqueue(node.right);
                        else
                            queue.Enqueue(null);
                    }
                    else
                    {
                        list.Append("null" + ",");
                    }

                }
                result.Append(list.ToString());
            }
            result.Remove(result.Length - 1, 1);
            return result.ToString();
        }

        // Decodes your encoded data to tree.
        public TreeNode deserialize(string data)
        {
            if (data.Length == 0)
                return null;
            Queue<TreeNode> queue = new Queue<TreeNode>();
            var tlist = data.Split(',');
            var count = tlist.Length;

            foreach (var l in tlist)
            {
                if (l != "null")
                {
                    var t = new TreeNode(int.Parse(l));
                    queue.Enqueue(t);
                }
                else
                {
                    queue.Enqueue(null);
                }
            }
            var root = queue.Dequeue();
            var list = new List<TreeNode>();
            list.Add(root);
            while (queue.Any())
            {
                var temp = new List<TreeNode>();
                for (int i = 0; i < list.Count; i++)
                {
                    var p = list[i];
                    var left = queue.Dequeue();
                    if (left != null)
                    {
                        p.left = left;
                    }
                    var right = queue.Dequeue();
                    if (right != null)
                    {
                        p.right = right;
                    }
                    if (p.left != null)
                    {
                        temp.Add(p.left);
                    }
                    if (p.right != null)
                    {
                        temp.Add(p.right);
                    }
                }
                list = temp;
            }
            return root;
        }
    }