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() == )
                     break;

                 int nodesAtLevel = queue.Count();
                 StringBuilder list = new StringBuilder();
                 for (int i = ; 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 - , );
             return result.ToString();
         }

         // Decodes your encoded data to tree.
         public TreeNode deserialize(string data)
         {
             if (data.Length == )
                 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 = ; 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;
         }
     }