297. Serialize and Deserialize Binary Tree.cpp

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 tree.
There is no restriction on how your serialization/deserialization algorithm should work.
You just need to ensure that a binary tree can be serialized to a string and this string can be deserialized to the original tree structure.

Example:

You may serialize the following tree:

    1
   / \
  2   3
     / \
    4   5

as "[1,2,3,null,null,4,5]"
Clarification: The above format is the same as how LeetCode serializes a binary tree.
You do not necessarily need to follow this format, so please be creative and come up with different approaches yourself.

Note: Do not use class member/global/static variables to store states.
Your serialize and deserialize algorithms should be stateless.






class Codec {
public:

    // Encodes a tree to a single string.
    string serialize(TreeNode* root) {
        if (root == NULL) return "#";
        return to_string(root->val) + "," + serialize(root->left) + "," + serialize(root->right);
    }

    TreeNode* deserialize(string data) {
        if (data == "#") return NULL;
        stringstream s(data);
        return makeDeserialize(s);
    }

    TreeNode* makeDeserialize(stringstream& s) {
        string str;
        getline(s, str, ',');
        if (str == "#") {
            return NULL;
        } else {
            TreeNode* root = new TreeNode(stoi(str));
            root->left = makeDeserialize(s);
            root->right = makeDeserialize(s);
            return root;
        }
    }
};