Serialize and Deserialize Binary Tree
<p>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.</p>

<p>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.</p>

<p><strong>Clarification:</strong> The input/output format is the same as <a href="https://support.leetcode.com/hc/en-us/articles/32442719377939-How-to-create-test-cases-on-LeetCode#h_01J5EGREAW3NAEJ14XC07GRW1A" target="_blank">how LeetCode serializes a binary tree</a>. You do not necessarily need to follow this format, so please be creative and come up with different approaches yourself.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://fastly.jsdelivr.net/gh/doocs/leetcode@main/solution/0200-0299/0297.Serialize%20and%20Deserialize%20Binary%20Tree/images/serdeser.jpg" style="width: 442px; height: 324px;" />
<pre>
<strong>Input:</strong> root = [1,2,3,null,null,4,5]
<strong>Output:</strong> [1,2,3,null,null,4,5]
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> root = []
<strong>Output:</strong> []
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li>The number of nodes in the tree is in the range <code>[0, 10<sup>4</sup>]</code>.</li>
	<li><code>-1000 &lt;= Node.val &lt;= 1000</code></li>
</ul>
Tree; Depth-First Search; Breadth-First Search; Design; String; Binary Tree
/**
 * 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 "";
        }
        queue<TreeNode*> q{{root}};
        string ans;
        while (!q.empty()) {
            auto node = q.front();
            q.pop();
            if (node) {
                ans += to_string(node->val) + " ";
                q.push(node->left);
                q.push(node->right);
            } else {
                ans += "# ";
            }
        }
        ans.pop_back();
        return ans;
    }

    // Decodes your encoded data to tree.
    TreeNode* deserialize(string data) {
        if (data == "") {
            return nullptr;
        }
        stringstream ss(data);
        string t;
        ss >> t;
        TreeNode* root = new TreeNode(stoi(t));
        queue<TreeNode*> q{{root}};
        while (!q.empty()) {
            auto node = q.front();
            q.pop();
            ss >> t;
            if (t != "#") {
                node->left = new TreeNode(stoi(t));
                q.push(node->left);
            }
            ss >> t;
            if (t != "#") {
                node->right = new TreeNode(stoi(t));
                q.push(node->right);
            }
        }
        return root;
    }
};

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