[leetcode] 297. Serialize and Deserialize Binary Tree 解题报告

最新推荐文章于 2022-05-31 22:37:22 发布

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最新推荐文章于 2022-05-31 22:37:22 发布

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本文介绍了如何实现LeetCode中297题的序列化和反序列化二叉树的算法。通过先根遍历进行序列化，并利用istringstream在C++中方便地处理字符串。解题思路和简洁的代码实现链接已给出。

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题目链接:https://leetcode.com/problems/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

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.

思路：使用先根遍历来序列化二叉树，然后再递归的解码字符串．在C++中有提供一个很方便做字符串处理的类，istringstream．有了这个类你就可以不用手动分割字符串了，在序列化的时候每个结点的值之间留一个空格，他就可以一个个的按照空格分割的方式将字符串一个个吐出来．很方便有没有！

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) {
        if(!root) return "#";
        string left = serialize(root->left), right = serialize(root->right);
        return to_string(root->val) + " " + left + " " + right;
    }

    // Decodes your encoded data to tree.
    TreeNode* deserialize(string data) {
        istringstream is(data);
        return DFS(is);
    }
    
    TreeNode* DFS(istringstream &is)
    {
        string val;
        is >> val;
        if(val == "#") return NULL;
        TreeNode *root = new TreeNode(stoi(val)), *left = DFS(is), *right = DFS(is);
        root->left = left, root->right = right;
        return root;
    }
};

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

参考:https://leetcode.com/discuss/76182/clean-c-solution

https://leetcode.com/discuss/66147/recursive-preorder-python-and-c-o-n