Deepest Leaves Sum
Given the <code>root</code> of a binary tree, return <em>the sum of values of its deepest leaves</em>.

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://fastly.jsdelivr.net/gh/doocs/leetcode@main/solution/1300-1399/1302.Deepest%20Leaves%20Sum/images/1483_ex1.png" style="width: 273px; height: 265px;" />
<pre>
<strong>Input:</strong> root = [1,2,3,4,5,null,6,7,null,null,null,null,8]
<strong>Output:</strong> 15
</pre>

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

<pre>
<strong>Input:</strong> root = [6,7,8,2,7,1,3,9,null,1,4,null,null,null,5]
<strong>Output:</strong> 19
</pre>

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

<ul>
	<li>The number of nodes in the tree is in the range <code>[1, 10<sup>4</sup>]</code>.</li>
	<li><code>1 &lt;= Node.val &lt;= 100</code></li>
</ul>
Tree; Depth-First Search; Breadth-First Search; Binary Tree
/**
 * Definition for a binary tree node.
 * class TreeNode {
 *     val: number
 *     left: TreeNode | null
 *     right: TreeNode | null
 *     constructor(val?: number, left?: TreeNode | null, right?: TreeNode | null) {
 *         this.val = (val===undefined ? 0 : val)
 *         this.left = (left===undefined ? null : left)
 *         this.right = (right===undefined ? null : right)
 *     }
 * }
 */

function deepestLeavesSum(root: TreeNode | null): number {
    let q: TreeNode[] = [root];
    let ans = 0;
    while (q.length) {
        const nq: TreeNode[] = [];
        ans = 0;
        for (const { val, left, right } of q) {
            ans += val;
            left && nq.push(left);
            right && nq.push(right);
        }
        q = nq;
    }
    return ans;
}
