[leetcode] 449. Serialize and Deserialize BST解題レポート

タイトルリンク:https://leetcode.com/problems/serialize-and-deserialize-bst/
Serialization is the process of converting a data structure or object into a sequence of bits so that it can be stored in a file or memory buffer, or transmitted across a network connection link to be reconstructed later in the same or another computer environment.
Design an algorithm to serialize and deserialize a binary search tree. There is no restriction on how your serialization/deserialization algorithm should work. You just need to ensure that a binary search tree can be serialized to a string and this string can be deserialized to the original tree structure.
The encoded string should be as compact as possible.
Note: Do not use class member/global/static variables to store states. Your serialize and deserialize algorithms should be stateless
考え方:c++の1つのクラスistringstreamと先根で昔からやります
コードは次のとおりです.

/**
 * 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 " #";
        string ans = " "+to_string(root->val);
        return ans + serialize(root->left) + serialize(root->right); 
    }

    TreeNode* DFS(istringstream &is)
    {
        string str;
        is >> str;
        if(str == "#") return NULL;
        TreeNode* root = new TreeNode(stoi(str));
        root->left = DFS(is), root->right = DFS(is);
        return root;
    }

    // Decodes your encoded data to tree.
    TreeNode* deserialize(string data) {
        istringstream is(data);
        return DFS(is);
    }
};

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