1
var isSameTree = function (p, q) {
2
  const stack = [p, q];
3

4
  while (stack.length) {
5
    const node2 = stack.pop();
6
    const node1 = stack.pop();
7

8
    if (!node1 && !node2) continue;
9

10
    if ((!node1 && node2) || (node1 && !node2) || node1.val !== node2.val) {
11
      return false;
12
    }
13

14
    stack.push(node1.left, node2.left, node1.right, node2.right);
15
  }
16

17
  return true;
18
};