Find Bottom Left Tree Value
<p>Given the <code>root</code> of a binary tree, return the leftmost value in the last row of the tree.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://fastly.jsdelivr.net/gh/doocs/leetcode@main/solution/0500-0599/0513.Find%20Bottom%20Left%20Tree%20Value/images/tree1.jpg" style="width: 302px; height: 182px;" />
<pre>
<strong>Input:</strong> root = [2,1,3]
<strong>Output:</strong> 1
</pre>

<p><strong class="example">Example 2:</strong></p>
<img alt="" src="https://fastly.jsdelivr.net/gh/doocs/leetcode@main/solution/0500-0599/0513.Find%20Bottom%20Left%20Tree%20Value/images/tree2.jpg" style="width: 432px; height: 421px;" />
<pre>
<strong>Input:</strong> root = [1,2,3,4,null,5,6,null,null,7]
<strong>Output:</strong> 7
</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>-2<sup>31</sup> &lt;= Node.val &lt;= 2<sup>31</sup> - 1</code></li>
</ul>
Tree; Depth-First Search; Breadth-First Search; Binary Tree
/**
 * Definition for a binary tree node.
 * type TreeNode struct {
 *     Val int
 *     Left *TreeNode
 *     Right *TreeNode
 * }
 */
func findBottomLeftValue(root *TreeNode) int {
	q := []*TreeNode{root}
	ans := 0
	for len(q) > 0 {
		ans = q[0].Val
		for i := len(q); i > 0; i-- {
			node := q[0]
			q = q[1:]
			if node.Left != nil {
				q = append(q, node.Left)
			}
			if node.Right != nil {
				q = append(q, node.Right)
			}
		}
	}
	return ans
}