反序列化二叉树的C++

struct TreeNode {
    int val;
    TreeNode* left;
    TreeNode* right;
    TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
};

class Solution {
public:
    TreeNode* deserialize(string data) {
        if (data.empty()) {
            return nullptr;
        }
        stringstream ss(data);
        return deserializeHelper(ss);
    }
    
private:
    TreeNode* deserializeHelper(stringstream& ss) {
        string val;
        getline(ss, val, ',');
        if (val == "#") {
            return nullptr;
        }
        TreeNode* root = new TreeNode(stoi(val));
        root->left = deserializeHelper(ss);
        root->right = deserializeHelper(ss);
        return root;
    }
};