Solution.cpp

/**
 * 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 "";
        }
        queue<TreeNode*> q{{root}};
        string ans;
        while (!q.empty()) {
            auto node = q.front();
            q.pop();
            if (node) {
                ans += to_string(node->val) + " ";
                q.push(node->left);
                q.push(node->right);
            } else {
                ans += "# ";
            }
        }
        ans.pop_back();
        return ans;
    }

    // Decodes your encoded data to tree.
    TreeNode* deserialize(string data) {
        if (data == "") {
            return nullptr;
        }
        stringstream ss(data);
        string t;
        ss >> t;
        TreeNode* root = new TreeNode(stoi(t));
        queue<TreeNode*> q{{root}};
        while (!q.empty()) {
            auto node = q.front();
            q.pop();
            ss >> t;
            if (t != "#") {
                node->left = new TreeNode(stoi(t));
                q.push(node->left);
            }
            ss >> t;
            if (t != "#") {
                node->right = new TreeNode(stoi(t));
                q.push(node->right);
            }
        }
        return root;
    }
};

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