297. Serialize and Deserialize Binary Tree

focusj 发布于2019-08-14 14:15 / 2008人阅读

摘要：题目解答用一个特殊的符号来表示的情况这是按先序遍历来存到中去这里用为其包含了几乎所有这里还是挺多知识点的，后是一个可以把数组变成则是把加到这个的中去

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 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

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

解答：

public class Codec {
    private String spliter = ",";
    //用一个特殊的符号来表示null的情况
    private String NN = "X";

    // Encodes a tree to a single string.
    public void BuildString(StringBuilder sb, TreeNode root) {
        if (root == null) {
            sb.append("X").append(spliter);
        } else {
            //这是按先序遍历来存root到string中去
            sb.append(root.val).append(spliter);
            BuildString(sb, root.left);
            BuildString(sb, root.right);
        }
    }
    
    public String serialize(TreeNode root) {
        StringBuilder sb = new StringBuilder();
        BuildString(sb, root);
        return sb.toString();
    }

    // Decodes your encoded data to tree.
    public TreeNode BuildTree(Deque nodes) {
        String node = nodes.remove();
        if (node.equals(NN)) {
            return null;
        } else {
            //Integer.valueOf("String");
            TreeNode root = new TreeNode(Integer.valueOf(node));
            root.left = BuildTree(nodes);
            root.right = BuildTree(nodes);
            return root;
        }
    }
    
    public TreeNode deserialize(String data) {
        //deque这里用linkedlist为interface,其包含了几乎所有resizable array
        Deque nodes = new LinkedList<>();
        //这里还是挺多知识点的，String.split()后是一个String[], Arrays.asList()可以把数组变成list, nodes.addAll()则是把list加到nodes这个list的中去
        nodes.addAll(Arrays.asList(data.split(spliter)));
        return BuildTree(nodes);
    }
}

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

GPU云服务器云服务器 binary-tree binary-search-tree Deserialize serialize

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