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.
 * function TreeNode(val) {
 *     this.val = val;
 *     this.left = this.right = null;
 * }
 */

/**
 * Encodes a tree to a single string.
 *
 * @param {TreeNode} root
 * @return {string}
 */
var serialize = function (root) {
    if (root === null) {
        return null;
    }
    const ans = [];
    const q = [root];
    let index = 0;
    while (index < q.length) {
        const node = q[index++];
        if (node !== null) {
            ans.push(node.val.toString());
            q.push(node.left);
            q.push(node.right);
        } else {
            ans.push('#');
        }
    }
    return ans.join(',');
};

/**
 * Decodes your encoded data to tree.
 *
 * @param {string} data
 * @return {TreeNode}
 */
var deserialize = function (data) {
    if (data === null) {
        return null;
    }
    const vals = data.split(',');
    let i = 0;
    const root = new TreeNode(parseInt(vals[i++]));
    const q = [root];
    let index = 0;
    while (index < q.length) {
        const node = q[index++];
        if (vals[i] !== '#') {
            node.left = new TreeNode(+vals[i]);
            q.push(node.left);
        }
        i++;
        if (vals[i] !== '#') {
            node.right = new TreeNode(+vals[i]);
            q.push(node.right);
        }
        i++;
    }
    return root;
};

/**
 * Your functions will be called as such:
 * deserialize(serialize(root));
 */
