✨ Iterative Algorithm
const bfs = (root) => {
const queue = [root];
let res = 0;
while (queue.length) {
const len = queue.length;
for (let i = 0; i < len; i += 1) {
const cur = queue.shift();
// do logic
if (node.left) queue.push(node.left);
if (node.right) queue.push(node.right);
}
}
};
return bfs(root);