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.

Clarification: The input/output format is the same as how LeetCode serializes a binary tree. You do not necessarily need to follow this format, so please be creative and come up with different approaches yourself.

 

Example 1:

Input: root = [1,2,3,null,null,4,5] Output: [1,2,3,null,null,4,5] Example 2:

Input: root = [] Output: []  

Constraints:

The number of nodes in the tree is in the range [0, 104]. -1000 <= Node.val <= 1000

Code

Time Complexity: $O(n)$, Space Complexity: $O(n)$

• Usage of C++ stringstream (delimiter default is a space)
• How to use stringstream to separate comma separated strings [duplicate]

關鍵在於利用 Preorder，怎麼樣 preorder serialize，就怎麼樣 preorder desirealize。

class Codec {
public:
 
    string serialize(TreeNode* root) {
        ostringstream out;
        serialize(root, out);
        return out.str();
    }
 
    TreeNode* deserialize(string data) {
        istringstream in(data);
        return deserialize(in);
    }
 
private:
 
    void serialize(TreeNode* root, ostringstream& out) {
        if (root) {
            out << root->val << ' ';
            serialize(root->left, out);
            serialize(root->right, out);
        } else {
            out << "# ";
        }
    }
 
    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;
    }
};

class Codec {
public:
 
    string serialize(TreeNode* root) {
        stringstream out;
        serialize(root, out);
        return out.str();
    }
 
    TreeNode* deserialize(string data) {
        stringstream in(data);
        return deserialize(in);
    }
 
private:
 
    void serialize(TreeNode* root, stringstream& out) {
        if (root) {
            out << root->val << ' ';
            serialize(root->left, out);
            serialize(root->right, out);
        } else {
            out << "# ";
        }
    }
 
    TreeNode* deserialize(stringstream& 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;
    }
};

Source

• Serialize and Deserialize Binary Tree - LeetCode