serializeandDeserializeBST.cpp

// Source: https://leetcode.com/problems/serialize-and-deserialize-bst/
// Author: Miao Zhang
// Date:   2021-02-12

/**
 * 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) {
        stringstream ss(data);
        return build(ss);
    }

private:
    TreeNode* build(stringstream& ss) {
        string elem;
        ss >> elem;
        if (elem == "#") return nullptr;
        TreeNode* root = new TreeNode(stoi(elem));
        root->left = build(ss);
        root->right = build(ss);
        return root;
    }
};

// Your Codec object will be instantiated and called as such:
// Codec* ser = new Codec();
// Codec* deser = new Codec();
// string tree = ser->serialize(root);
// TreeNode* ans = deser->deserialize(tree);
// return ans;