297. Serialize and Deserialize Binary Tree

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


// Acception of others ! should study in detail!
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;
    }
};