297 Serialize and Deserialize Binary Tree

297. Serialize and Deserialize Binary Tree​
1. Question
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
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    1
2
   / \
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  2   3
4
     / \
5
    4   5
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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.
2. Implementation
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/**
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 * Definition for a binary tree node.
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 * public class TreeNode {
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 *     int val;
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 *     TreeNode left;
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 *     TreeNode right;
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 *     TreeNode(int x) { val = x; }
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 * }
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 */
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public class Codec {
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​
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    // Encodes a tree to a single string.
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    public String serialize(TreeNode root) {
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        StringBuilder res = new StringBuilder();
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        convertToString(root, res);
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        return res.toString();
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    }
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​
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    public void convertToString(TreeNode node, StringBuilder res) {
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        if (node == null) {
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            res.append("#").append(",");
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        }
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        else {
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            res.append(node.val).append(",");
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            convertToString(node.left, res);
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            convertToString(node.right, res);
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        }
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    }
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​
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    // Decodes your encoded data to tree.
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    public TreeNode deserialize(String data) {
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        Queue<String> queue = new LinkedList<>();
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        queue.addAll(Arrays.asList(data.split(",")));
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        return buildTree(queue);
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    }
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​
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    public TreeNode buildTree(Queue<String> queue) {
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        String val = queue.remove();
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        if (val.equals("#")) {
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            return null;
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        }
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        TreeNode node = new TreeNode(Integer.valueOf(val));
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        node.left = buildTree(queue);
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        node.right = buildTree(queue);
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        return node;
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    }
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}
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​
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// Your Codec object will be instantiated and called as such:
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// Codec codec = new Codec();
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// codec.deserialize(codec.serialize(root));
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3. Time & Space Complexity
时间复杂度O(n), 空间复杂度O(n)

314 Binary Tree Vertical Order Traversal

447 Number of Boomerangs

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Contents

297. Serialize and Deserialize Binary Tree

1. Question

2. Implementation

3. Time & Space Complexity

297. Serialize and Deserialize Binary Tree​

1. Question

2. Implementation

3. Time & Space Complexity

297. Serialize and Deserialize Binary Tree