LeetCode 树序列化与反序列化[递归]297. Serialize and Deserialize Binary Tree

题目链接

https://leetcode.com/problems/serialize-and-deserialize-binary-tree/#/description

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.

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

递归代码如下：

/** * Definition for a binary tree node. * struct TreeNode { *     int val; *     TreeNode *left; *     TreeNode *right; *     TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */class Codec {public:    // Encodes a tree to a single string.    string serialize(TreeNode* root) {        ostringstream s;        serialize(root, s);        return s.str();    }    // Decodes your encoded data to tree.    TreeNode* deserialize(string data) {        istringstream in(data);        return deserialize(in);    }private:    void serialize(TreeNode *root, ostringstream &s) {        if (root) {            s << root->val << ' ';            serialize(root->left, s);            serialize(root->right, s);        } else {            s << "# ";        }    }    TreeNode* deserialize(istringstream &in) {        string val;        in >> val;        if (val == "#") return nullptr;        TreeNode *root = new TreeNode(stoi(val));        root->left = deserialize(in);        root->right = deserialize(in);        return root;    }};// Your Codec object will be instantiated and called as such:// Codec codec;// codec.deserialize(codec.serialize(root));