Serialize and Deserialize Binary Tree

Serialization is the process of converting a data structure or object into a sequence of bits so that it can be stored in a file or memory buffer, or transmitted across a network connection link to be reconstructed later in the same or another computer environment.

Design an algorithm to serialize and deserialize a binary tree. There is no restriction on how your serialization/deserialization algorithm should work. You just need to ensure that a binary tree can be serialized to a string and this string can be deserialized to the original tree structure.

For example, you may serialize the following tree

    1
   / \
  2   3
     / \
    4   5

as "[1,2,3,null,null,4,5]", just the same as how LeetCode OJ serializes a binary tree. You do not necessarily need to follow this format, so please be creative and come up with different approaches yourself.

 

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Codec {

    // Encodes a tree to a single string.
    public String serialize(TreeNode root) {
        if (root == null) {
        	return "#!";
        }
        String res = root.val + "!";
        res += serialize(root.left);
        res += serialize(root.right);
        return res;
    }

    // Decodes your encoded data to tree.
    public TreeNode deserialize(String data) {
    	String[] split = data.split("!");
    	LinkedList<String> queue = new LinkedList<>();
    	for (int i = 0; i < split.length; i++) {
    		queue.offer(split[i]);
		}
    	return reconPreOrder(queue);
    }

	private TreeNode reconPreOrder(LinkedList<String> queue) {
		// TODO Auto-generated method stub
		String poll = queue.poll();
		if (poll.equals("#")) {
			return null;
		}
		TreeNode head = new TreeNode(Integer.valueOf(poll));
		head.left = reconPreOrder(queue);
		head.right = reconPreOrder(queue);
		return head;
	}
}

// Your Codec object will be instantiated and called as such:
// Codec codec = new Codec();
// codec.deserialize(codec.serialize(root));