# Given a binary tree, connect each node with its level order successor.
# The last node of each level should point to the first node of the next level.
# O(N) space:O(N)
from collections import deque
class TreeNode:
def __init__(self, value) -> None:
self.value = value
self.left = None
self.right = None
self.next = None
def print_tree(self):
current = self
while current:
print(str(current.value) + " ", end = "")
current = current.next
print()
def connect_all_level_order_siblings(root):
if root is None:
return
queue = deque()
queue.append(root)
previous_node = None
while queue:
current_node = queue.popleft()
if previous_node:
previous_node.next = current_node
previous_node = current_node
if current_node.left:
queue.append(current_node.left)
if current_node.right:
queue.append(current_node.right)
return
root = TreeNode(12)
root.left = TreeNode(7)
root.right = TreeNode(1)
root.left.left = TreeNode(9)
root.right.left = TreeNode(10)
root.right.right = TreeNode(5)
connect_all_level_order_siblings(root)
root.print_tree()