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add binary_tree_traversals.py to data_structures (#3297)

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* add binary_tree_traversals.py to data_structures

I have added some interesting binary tree traversing methods.

* Fixed error

* Update data_structures/binary_tree/binary_tree_traversals.py

Co-authored-by: Christian Clauss <cclauss@me.com>

* Update binary_tree_traversals.py

* Update binary_tree_traversals.py

* Update binary_tree_traversals.py

* Update data_structures/binary_tree/binary_tree_traversals.py

Co-authored-by: Christian Clauss <cclauss@me.com>

* Update binary_tree_traversals.py

* Update binary_tree_traversals.py

* Update binary_tree_traversals.py

* Update binary_tree_traversals.py

* Update binary_tree_traversals.py

* Update binary_tree_traversals.py

* Update binary_tree_traversals.py

* Update binary_tree_traversals.py

* Update binary_tree_traversals.py

* Update binary_tree_traversals.py

* Update data_structures/binary_tree/binary_tree_traversals.py

Co-authored-by: Christian Clauss <cclauss@me.com>

* Update binary_tree_traversals.py

* Update binary_tree_traversals.py

* Update data_structures/binary_tree/binary_tree_traversals.py

Co-authored-by: Christian Clauss <cclauss@me.com>

* Update data_structures/binary_tree/binary_tree_traversals.py

Co-authored-by: Christian Clauss <cclauss@me.com>

* Update binary_tree_traversals.py

* Update data_structures/binary_tree/binary_tree_traversals.py

Co-authored-by: Christian Clauss <cclauss@me.com>

* Update binary_tree_traversals.py

* Doctests and type hints

* Add spaces

* Update binary_tree_traversals.py

* black exclude data_structures/binary_tree/binary_tree_traversals.py

* Add spaces again

* Update binary_tree_traversals.py

Co-authored-by: Christian Clauss <cclauss@me.com>
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.pre-commit-config.yaml
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@ -18,6 +18,10 @@ repos:
rev: stable
hooks:
- id: black
exclude: |
(?x)^(
data_structures/binary_tree/binary_tree_traversals.py
)$
- repo: https://github.com/PyCQA/isort
rev: 5.5.3
hooks:

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data_structures/binary_tree/binary_tree_traversals.py Normal file
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# https://en.wikipedia.org/wiki/Tree_traversal
class Node:
"""
A Node has data variable and pointers to its left and right nodes.
"""
def __init__(self, data):
self.left = None
self.right = None
self.data = data
def make_tree() -> Node:
root = Node(1)
root.left = Node(2)
root.right = Node(3)
root.left.left = Node(4)
root.left.right = Node(5)
return root
def preorder(root: Node):
"""
Pre-order traversal visits root node, left subtree, right subtree.
>>> preorder(make_tree())
[1, 2, 4, 5, 3]
"""
return [root.data] + preorder(root.left) + preorder(root.right) if root else []
def postorder(root: Node):
"""
Post-order traversal visits left subtree, right subtree, root node.
>>> postorder(make_tree())
[4, 5, 2, 3, 1]
"""
return postorder(root.left) + postorder(root.right) + [root.data] if root else []
def inorder(root: Node):
"""
In-order traversal visits left subtree, root node, right subtree.
>>> inorder(make_tree())
[4, 2, 5, 1, 3]
"""
return inorder(root.left) + [root.data] + inorder(root.right) if root else []
def height(root: Node):
"""
Recursive function for calculating the height of the binary tree.
>>> height(None)
0
>>> height(make_tree())
3
"""
return (max(height(root.left), height(root.right)) + 1) if root else 0
def level_order_1(root: Node):
"""
Print whole binary tree in Level Order Traverse.
Level Order traverse: Visit nodes of the tree level-by-level.
"""
if not root:
return
temp = root
que = [temp]
while len(que) > 0:
print(que[0].data, end=" ")
temp = que.pop(0)
if temp.left:
que.append(temp.left)
if temp.right:
que.append(temp.right)
return que
def level_order_2(root: Node, level: int):
"""
Level-wise traversal: Print all nodes present at the given level of the binary tree
"""
if not root:
return root
if level == 1:
print(root.data, end=" ")
elif level > 1:
level_order_2(root.left, level - 1)
level_order_2(root.right, level - 1)
def print_left_to_right(root: Node, level: int):
"""
Print elements on particular level from left to right direction of the binary tree.
"""
if not root:
return
if level == 1:
print(root.data, end=" ")
elif level > 1:
print_left_to_right(root.left, level - 1)
print_left_to_right(root.right, level - 1)
def print_right_to_left(root: Node, level: int):
"""
Print elements on particular level from right to left direction of the binary tree.
"""
if not root:
return
if level == 1:
print(root.data, end=" ")
elif level > 1:
print_right_to_left(root.right, level - 1)
print_right_to_left(root.left, level - 1)
def zigzag(root: Node):
"""
ZigZag traverse: Print node left to right and right to left, alternatively.
"""
flag = 0
height_tree = height(root)
for h in range(1, height_tree + 1):
if flag == 0:
print_left_to_right(root, h)
flag = 1
else:
print_right_to_left(root, h)
flag = 0
def main(): # Main function for testing.
"""
Create binary tree.
"""
root = make_tree()
"""
All Traversals of the binary are as follows:
"""
print(f" In-order Traversal is {inorder(root)}")
print(f" Pre-order Traversal is {preorder(root)}")
print(f"Post-order Traversal is {postorder(root)}")
print(f"Height of Tree is {height(root)}")
print("Complete Level Order Traversal is : ")
level_order_1(root)
print("\nLevel-wise order Traversal is : ")
for h in range(1, height(root) + 1):
level_order_2(root, h)
print("\nZigZag order Traversal is : ")
zigzag(root)
print()
if __name__ == "__main__":
import doctest
doctest.testmod()
main()