LeetCode 449. Serialize and Deserialize BST

原题链接在这里：https://leetcode.com/problems/serialize-and-deserialize-bst/description/

题目：

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

The encoded string should be as compact as possible.

Note: Do not use class member/global/static variables to store states. Your serialize and deserialize algorithms should be stateless.

题解：

与Serialize and Deserialize Binary Tree相同解法.

Time Complexity: serialize, O(n). deserialize, O(n). Space: O(n).

AC Java:

/**
 * 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) {
        StringBuilder sb = new StringBuilder();
        preorder(root, sb);
        return sb.toString();
    }
    
    private void preorder(TreeNode root, StringBuilder sb){
        if(root == null){
            sb.append("#").append(",");
            return;
        }
        sb.append(root.val).append(",");
        preorder(root.left, sb);
        preorder(root.right, sb);
    }

    // Decodes your encoded data to tree.
    public TreeNode deserialize(String data) {
        LinkedList<String> que = new LinkedList<String>();
        que.addAll(Arrays.asList(data.split(",")));
        return deserial(que);
    }
    
    private TreeNode deserial(LinkedList<String> que){
        String str = que.pollFirst();
        if(str.equals("#")){
            return null;
        }
        TreeNode root = new TreeNode(Integer.valueOf(str));
        root.left = deserial(que);
        root.right = deserial(que);
        return root;
    }
}

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