二叉树的序列化和反序列化

设计一个算法，并编写代码来序列化和反序列化二叉树。将树写入一个文件被称为“序列化”，读取文件后重建同样的二叉树被称为“反序列化”。

如何反序列化或序列化二叉树是没有限制的，你只需要确保可以将二叉树序列化为一个字符串，并且可以将字符串反序列化为原来的树结构。

/**

* Definition of TreeNode:

* public class TreeNode {

*    public int val;

*    public TreeNode left, right;

*    public TreeNode(int val) {

*        this.val = val;

*        this.left = this.right = null;

*    }

* }

*/

class Solution {

    /**

    * This method will be invoked first, you should design your own algorithm

    * to serialize a binary tree which denote by a root node to a string which

    * can be easily deserialized by your own "deserialize" method later.

    */

    public String serialize(TreeNode root) {

        // write your code here

        Queue queue = new LinkedList();

        queue.offer(root);

        StringBuilder builder = new StringBuilder();

        while(!queue.isEmpty()){

            TreeNode node = queue.poll();

            if(null == node){

                builder.append("#,");

            }else{

                builder.append(node.val+",");

                queue.offer(node.left);

                queue.offer(node.right);

            }

        }

        return builder.toString().substring(0,builder.length()-1);

    }

    /**

    * This method will be invoked second, the argument data is what exactly

    * you serialized at method "serialize", that means the data is not given by

    * system, it's given by your own serialize method. So the format of data is

    * designed by yourself, and deserialize it here as you serialize it in

    * "serialize" method.

    */

    public TreeNode deserialize(String data) {

        // write your code here

        if(data == null || "#".equals(data))

            return null ;

        String [] dataArray = data.split(",");

        TreeNode root = new TreeNode(Integer.parseInt(dataArray[0]+""));

        Queue queue = new LinkedList();

        queue.offer(root);

        for(int i = 1; i< dataArray.length; i = i+2){

            String left = dataArray[i];

            String right =dataArray[i+1];

            TreeNode leftNode = ("#".equals(left) ? null :new TreeNode(Integer.parseInt(dataArray[i]+"")) );

            TreeNode rightNode = ("#".equals(right) ? null :new TreeNode(Integer.parseInt(dataArray[i+1]+"")) );

            TreeNode temp = queue.poll();

            temp.left = leftNode;

            temp.right = rightNode;

            if(leftNode != null){

                queue.offer(leftNode);

            }

            if(rightNode !=null){

                queue.offer(rightNode);

            }

        }

        return root;

    }

}