level_order_traversal.py

# Python program to print level order traversal using Queue

# Time Complexity: O(n)
# Space Complexity: O(n)


# A node structure
class Node:
	# A utility function to create a new node
	def __init__(self, key):
		self.data = key
		self.left = None
		self.right = None

# Iterative Method to print the height of a binary tree
def printLevelOrder(root):
	# Base Case
	if root is None:
		return

	# Create an empty queue
	# for level order traversal
	queue = []

	# Enqueue Root and initialize height
	queue.append(root)

	while(len(queue) > 0):

		# Print front of queue and
		# remove it from queue
		print(queue[0].data, end = " ")
		node = queue.pop(0)

		# Enqueue left child
		if node.left is not None:
			queue.append(node.left)

		# Enqueue right child
		if node.right is not None:
			queue.append(node.right)


# Driver Program to test above function
root = Node(1)
root.left = Node(2)
root.right = Node(3)
root.left.left = Node(4)
root.left.right = Node(5)
root.right.left = Node(6)
root.right.right = Node(7)
root.right.left.right = Node(8)
root.right.right.right = Node(9)

print("Level Order Traversal of binary tree is -")
printLevelOrder(root)