剑指offer：面试题37. 序列化二叉树

题目：序列化二叉树

请实现两个函数，分别用来序列化和反序列化二叉树。

示例: 

你可以将以下二叉树：

    1
   / \
  2   3
     / \
    4   5

序列化为 "[1,2,3,null,null,4,5]"

---

解题：

/**
 * 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 {
private:
    // 1,2,#,#,3,-4,#,#,5,#,#,
    void encode(TreeNode* root, string& res) {
        if (!root) {
            res += "#,";
            return;
        }
        res += to_string(root->val) + ",";
        encode(root->left, res);
        encode(root->right, res);
    }
    
    TreeNode* decode(int& p, const string& data) {
        if (data[p] == '#') {
            p += 2;
            return NULL;
        }
        bool isN = false;
        if (data[p] == '-') {  // 负数的情况
            isN = true;
            p++;
        }
        int num = 0;  // 还原成整数
        while (data[p] != ',') {
            num = num * 10 + data[p] - '0';
            p++;
        }
        p++;
        if (isN) num = -num;
        
        auto root = new TreeNode(num);
        root->left = decode(p, data);
        root->right = decode(p, data);
        
        return root;
    }
    
public:

    // Encodes a tree to a single string.
    string serialize(TreeNode* root) {
        string res = "";
        encode(root, res);
        return res;
    }

    // Decodes your encoded data to tree.
    TreeNode* deserialize(string data) {
        int p = 0;
        return decode(p, data);
    }
};

 

来源：CSDN

作者：CG&AR Player

链接：https://blog.csdn.net/qq_41598072/article/details/104598811