All Elements in Two Binary Search Trees
<p>Given two binary search trees <code>root1</code> and <code>root2</code>, return <em>a list containing all the integers from both trees sorted in <strong>ascending</strong> order</em>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://fastly.jsdelivr.net/gh/doocs/leetcode@main/solution/1300-1399/1305.All%20Elements%20in%20Two%20Binary%20Search%20Trees/images/q2-e1.png" style="width: 457px; height: 207px;" />
<pre>
<strong>Input:</strong> root1 = [2,1,4], root2 = [1,0,3]
<strong>Output:</strong> [0,1,1,2,3,4]
</pre>

<p><strong class="example">Example 2:</strong></p>
<img alt="" src="https://fastly.jsdelivr.net/gh/doocs/leetcode@main/solution/1300-1399/1305.All%20Elements%20in%20Two%20Binary%20Search%20Trees/images/q2-e5-.png" style="width: 352px; height: 197px;" />
<pre>
<strong>Input:</strong> root1 = [1,null,8], root2 = [8,1]
<strong>Output:</strong> [1,1,8,8]
</pre>

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

<ul>
	<li>The number of nodes in each tree is in the range <code>[0, 5000]</code>.</li>
	<li><code>-10<sup>5</sup> &lt;= Node.val &lt;= 10<sup>5</sup></code></li>
</ul>
Tree; Depth-First Search; Binary Search Tree; Binary Tree; Sorting
/**
 * 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 getAllElements(root1: TreeNode | null, root2: TreeNode | null): number[] {
    const dfs = (root: TreeNode | null, nums: number[]) => {
        if (!root) {
            return;
        }
        dfs(root.left, nums);
        nums.push(root.val);
        dfs(root.right, nums);
    };
    const a: number[] = [];
    const b: number[] = [];
    dfs(root1, a);
    dfs(root2, b);
    const [m, n] = [a.length, b.length];
    const ans: number[] = [];
    let [i, j] = [0, 0];
    while (i < m && j < n) {
        if (a[i] < b[j]) {
            ans.push(a[i++]);
        } else {
            ans.push(b[j++]);
        }
    }
    while (i < m) {
        ans.push(a[i++]);
    }
    while (j < n) {
        ans.push(b[j++]);
    }
    return ans;
}
