C++ Super Simple, Clean & Short Soluion only 11 lines!
\nclass Codec {\npublic:\n\n    string serialize(TreeNode* root) \n    {\n        return !root ? " null" : " " + to_string(root->val) + serialize(root->left) + 
```\nclass Codec {\npublic:\n\n    string serialize(TreeNode* root) \n    {\n        return !root ? " null" : " " + to_string(root->val) + serialize(root->left) + serialize(root->right);\n    }\n\t\n    TreeNode* deserialize(string data) \n    {\n        istringstream ss(data);\n\t\treturn buildBST(ss);\n    }\n    \nprivate:\n    \n    TreeNode* buildBST(istringstream& ss)\n    {\n        string s;\n        ss >> s;\n        \n        if (s == "null")\n\t\t\treturn NULL;\n        \n        TreeNode* node = new TreeNode(stoi(s));\n        node->left = buildBST(ss);\n        node->right = buildBST(ss);\n            \n        return node;\n    }\n};\n```
['C']