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.
 * public class TreeNode {
 *     public int val;
 *     public TreeNode left;
 *     public TreeNode right;
 *     public TreeNode(int x) { val = x; }
 * }
 */
public class Codec {

    // Encodes a tree to a single string.
    public string serialize(TreeNode root) {
        if (root == null) {
            return null;
        }
        List<string> ans = new List<string>();
        Queue<TreeNode> q = new Queue<TreeNode>();
        q.Enqueue(root);
        while (q.Count > 0) {
            TreeNode node = q.Dequeue();
            if (node != null) {
                ans.Add(node.val.ToString());
                q.Enqueue(node.left);
                q.Enqueue(node.right);
            } else {
                ans.Add("#");
            }
        }
        return string.Join(",", ans);
    }

    // Decodes your encoded data to tree.
    public TreeNode deserialize(string data) {
        if (data == null) {
            return null;
        }
        string[] vals = data.Split(',');
        int i = 0;
        TreeNode root = new TreeNode(int.Parse(vals[i++]));
        Queue<TreeNode> q = new Queue<TreeNode>();
        q.Enqueue(root);
        while (q.Count > 0) {
            TreeNode node = q.Dequeue();
            if (vals[i] != "#") {
                node.left = new TreeNode(int.Parse(vals[i]));
                q.Enqueue(node.left);
            }
            i++;
            if (vals[i] != "#") {
                node.right = new TreeNode(int.Parse(vals[i]));
                q.Enqueue(node.right);
            }
            i++;
        }
        return root;
    }
}

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