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traversals.py
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traversals.py
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from Tree.commons import insert, print_tree, is_leaf
def preorder(root):
if root:
print(root.key, end=',')
preorder(root.left)
preorder(root.right)
def inorder(root):
if root:
inorder(root.left)
print(root.key, end=',')
inorder(root.right)
def postorder(root):
if root:
postorder(root.left)
postorder(root.right)
print(root.key, end=',')
def level_order(root):
from queue import Queue
q = Queue()
q.put(root)
while not q.empty():
popped_elt = q.get()
print(popped_elt.key, end=',')
if popped_elt.left: q.put(popped_elt.left)
if popped_elt.right: q.put(popped_elt.right)
def spiral(root):
stack1 = [root]
stack2 = []
while len(stack1) or len(stack2):
while len(stack1):
popped_node = stack1.pop()
print(popped_node.key, end=',')
# left first then right
if popped_node.left is not None: stack2.append(popped_node.left)
if popped_node.right is not None: stack2.append(popped_node.right)
while len(stack2):
popped_node = stack2.pop()
print(popped_node.key, end=',')
# right first then left
if popped_node.right is not None: stack1.append(popped_node.right)
if popped_node.left is not None: stack1.append(popped_node.left)
# Driver program to test above function
if __name__ == "__main__":
""" Let us create following BST
50
/ \
30 70
/ \ / \
20 40 60 80
"""
root = None
root = insert(root, 50)
insert(root, 30)
insert(root, 20)
insert(root, 40)
insert(root, 70)
insert(root, 60)
insert(root, 80)
print("In-Order is - ")
inorder(root)
print("\nPre-Order is - ")
preorder(root)
print("\nPost-Order is - ")
postorder(root)
print("\nLevel-Order is - ")
level_order(root)
print("\nSprial(zig-zag)-Order is - ")
spiral(root)