Daily Interview Problem: Full Binary Tree

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

Given a binary tree, remove the nodes in which there is only 1 child, so that the binary tree is a full binary tree.

So leaf nodes with no children should be kept, and nodes with 2 children should be kept as well.

Here's a starting point:

from collections import deque



class Node(object):

  def __init__(self, value, left=None, right=None):

    self.left = left

    self.right = right

    self.value = value

  def __str__(self):

    q = deque()

    q.append(self)

    result = ''

    while len(q):

      num = len(q)

      while num > 0:

        n = q.popleft()

        result += str(n.value)

        if n.left:

          q.append(n.left)

        if n.right:

          q.append(n.right)

        num = num - 1

      if len(q):

        result += "\n"



    return result



def fullBinaryTree(node):

  # Fill this in.



# Given this tree:

#     1

#    / \ 

#   2   3

#  /   / \

# 0   9   4



# We want a tree like:

#     1

#    / \ 

#   0   3

#      / \

#     9   4



tree = Node(1)

tree.left = Node(2)

tree.right = Node(3)

tree.right.right = Node(4)

tree.right.left = Node(9)

tree.left.left = Node(0)

print fullBinaryTree(tree)

# 1

# 03

# 94