<pre class="shiki github-dark shaku"><code>/** * @param {HTMLElement | null} root * @return {HTMLElement[]} */function flatten(root) { // your code here let output = [] function traverse(nodes) { if (!nodes) { return } let queue = [nodes] while (queue.length) { let node = queue.shift() output.push(node) for (const child of node.children) { queue.push(child) } } } traverse(root) return output}</code></pre>

O(N)

Amazon

Given a DOM tree, flatten it into an one dimensional array, in the order of layer by layer, like below. [https://cdn.bfe.dev/bfe/img/ykqFdOIOaXFyn2uZ8…