binaryTreeEqual

// interface TreeNode {
//   val: number;
//   left: TreeNode | null;
//   right: TreeNode | null;
// }

/**
 * Time: O(n)
 * Space: O(n) in the worst case for the queue.
 */
/**
 * Returns true if two binary trees are identical.
 */
function binaryTreeEqual(
  // a: TreeNode | null,
  // b: TreeNode | null,
  a, b
) {
  // Both nodes are empty
  if (a === null && b === null) {
    return true;
  }

  // One node exists, the other doesn't
  if (a === null || b === null) {
    return false;
  }

  // Values differ
  if (a.val !== b.val) {
    return false;
  }

  // Compare left and right subtrees
  return (
    binaryTreeEqual(a.left, b.left) &&
    binaryTreeEqual(a.right, b.right)
  );
}