Hi, here's your problem today. This problem was recently asked by Microsoft:

Given the root of a binary tree, print its level-order traversal. For example:

<pre>
  1
 / \
2   3
   / \
  4   5
</pre>

The following tree should output 1, 2, 3, 4, 5.

<pre lang=py>
class Node:
  def __init__(self, val, left=None, right=None):
    self.val = val
    self.left = left
    self.right = right

def print_level_order(root):
  # Fill this in.

root = Node(1, Node(2), Node(3, Node(4), Node(5)))
print_level_order(root)
# 1 2 3 4 5
</pre>