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

You are given the root of a binary tree. Return the deepest node (the furthest node from the root).

Example:

<pre>
    a
   / \
  b   c
 /
d
</pre>

The deepest node in this tree is d at depth 3.

Here's a starting point:

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

  def __repr__(self):
    # string representation
    return self.val


def deepest(node):
  # Fill this in.

root = Node('a')
root.left = Node('b')
root.left.left = Node('d')
root.right = Node('c')

print deepest(root)
# (d, 3)
</pre>