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

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

    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.

思路:几个月之前尝试过写这题,写了一半放弃了,现在看了之前的代码,真是蠢哭了,我居然真的就按提示去用层次遍历的方式去序列化树了.

而其实比较方便的序列化的方式应该是树的中序方式了.然后重建树的时候我们可以利用C++中提供的一个极其方便的类istringstream来每次移动输出一个结点值,简直神器.可以极大简化代码.

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 "#";
        return to_string(root->val)+ " " + serialize(root->left) + " " + serialize(root->right);
    }

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

// 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