?LeetCode刷題實(shí)戰(zhàn)449：序列化和反序列化二叉搜索樹

示例 1：
輸入：root = [2,1,3]
輸出：[2,1,3]

示例 2：
輸入：root = []
輸出：[]

/**
?* 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 == NULL) { // 空節(jié)點(diǎn)用"#"表示
???????????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?decode(ss);
????}

????TreeNode* decode(stringstream?&ss)?{
????????string?data;
????????ss >> data;
????????if(data == "#") { 
????????????return?NULL;
????????}
????????TreeNode* root = new?TreeNode(stoi(data)); // stringstream讀到的第一段字符串是根節(jié)點(diǎn)的值
????????root -> left = decode(ss); // 遞歸調(diào)用decode()方法對左右子樹建樹，并將root與左右子樹連接起來
????????root -> right = decode(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;