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Add type hints to binary_tree_traversals.py #1123

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Aug 12, 2019
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Add type hints to binary_tree_traversals.py #1123

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103 changes: 50 additions & 53 deletions traversals/binary_tree_traversals.py
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Original file line number Diff line number Diff line change
@@ -1,14 +1,8 @@
"""
This is pure python implementation of tree traversal algorithms
"""
from __future__ import print_function

import queue

try:
raw_input # Python 2
except NameError:
raw_input = input # Python 3
from typing import List


class TreeNode:
Expand All @@ -20,62 +14,58 @@ def __init__(self, data):

def build_tree():
print("\n********Press N to stop entering at any point of time********\n")
print("Enter the value of the root node: ", end="")
check = raw_input().strip().lower()
if check == 'n':
check = input("Enter the value of the root node: ").strip().lower() or "n"
if check == "n":
return None
data = int(check)
q = queue.Queue()
tree_node = TreeNode(data)
q: queue.Queue = queue.Queue()
tree_node = TreeNode(int(check))
q.put(tree_node)
while not q.empty():
node_found = q.get()
print("Enter the left node of %s: " % node_found.data, end="")
check = raw_input().strip().lower()
if check == 'n':
msg = "Enter the left node of %s: " % node_found.data
check = input(msg).strip().lower() or "n"
if check == "n":
return tree_node
left_data = int(check)
left_node = TreeNode(left_data)
left_node = TreeNode(int(check))
node_found.left = left_node
q.put(left_node)
print("Enter the right node of %s: " % node_found.data, end="")
check = raw_input().strip().lower()
if check == 'n':
msg = "Enter the right node of %s: " % node_found.data
check = input(msg).strip().lower() or "n"
if check == "n":
return tree_node
right_data = int(check)
right_node = TreeNode(right_data)
right_node = TreeNode(int(check))
node_found.right = right_node
q.put(right_node)


def pre_order(node):
def pre_order(node: TreeNode) -> None:
if not isinstance(node, TreeNode) or not node:
return
print(node.data, end=" ")
pre_order(node.left)
pre_order(node.right)


def in_order(node):
def in_order(node: TreeNode) -> None:
if not isinstance(node, TreeNode) or not node:
return
in_order(node.left)
print(node.data, end=" ")
in_order(node.right)


def post_order(node):
def post_order(node: TreeNode) -> None:
if not isinstance(node, TreeNode) or not node:
return
post_order(node.left)
post_order(node.right)
print(node.data, end=" ")


def level_order(node):
def level_order(node: TreeNode) -> None:
if not isinstance(node, TreeNode) or not node:
return
q = queue.Queue()
q: queue.Queue = queue.Queue()
q.put(node)
while not q.empty():
node_dequeued = q.get()
Expand All @@ -86,10 +76,10 @@ def level_order(node):
q.put(node_dequeued.right)


def level_order_actual(node):
def level_order_actual(node: TreeNode) -> None:
if not isinstance(node, TreeNode) or not node:
return
q = queue.Queue()
q: queue.Queue = queue.Queue()
q.put(node)
while not q.empty():
list = []
Expand All @@ -106,10 +96,10 @@ def level_order_actual(node):


# iteration version
def pre_order_iter(node):
def pre_order_iter(node: TreeNode) -> None:
if not isinstance(node, TreeNode) or not node:
return
stack = []
stack: List[TreeNode] = []
n = node
while n or stack:
while n: # start from root node, find its left child
Expand All @@ -122,10 +112,10 @@ def pre_order_iter(node):
n = n.right


def in_order_iter(node):
def in_order_iter(node: TreeNode) -> None:
if not isinstance(node, TreeNode) or not node:
return
stack = []
stack: List[TreeNode] = []
n = node
while n or stack:
while n:
Expand All @@ -136,7 +126,7 @@ def in_order_iter(node):
n = n.right


def post_order_iter(node):
def post_order_iter(node: TreeNode) -> None:
if not isinstance(node, TreeNode) or not node:
return
stack1, stack2 = [], []
Expand All @@ -153,38 +143,45 @@ def post_order_iter(node):
print(stack2.pop().data, end=" ")


if __name__ == '__main__':
print("\n********* Binary Tree Traversals ************\n")
def prompt(s: str = "", width=50, char="*") -> str:
if not s:
return "\n" + width * char
left, extra = divmod(width - len(s) - 2, 2)
return f"{left * char} {s} {(left + extra) * char}"


if __name__ == "__main__":
print(prompt("Binary Tree Traversals"))

node = build_tree()
print("\n********* Pre Order Traversal ************")
print(prompt("Pre Order Traversal"))
pre_order(node)
print("\n******************************************\n")
print(prompt() + "\n")

print("\n********* In Order Traversal ************")
print(prompt("In Order Traversal"))
in_order(node)
print("\n******************************************\n")
print(prompt() + "\n")

print("\n********* Post Order Traversal ************")
print(prompt("Post Order Traversal"))
post_order(node)
print("\n******************************************\n")
print(prompt() + "\n")

print("\n********* Level Order Traversal ************")
print(prompt("Level Order Traversal"))
level_order(node)
print("\n******************************************\n")
print(prompt() + "\n")

print("\n********* Actual Level Order Traversal ************")
print(prompt("Actual Level Order Traversal"))
level_order_actual(node)
print("\n******************************************\n")
print("*" * 50 + "\n")

print("\n********* Pre Order Traversal - Iteration Version ************")
print(prompt("Pre Order Traversal - Iteration Version"))
pre_order_iter(node)
print("\n******************************************\n")
print(prompt() + "\n")

print("\n********* In Order Traversal - Iteration Version ************")
print(prompt("In Order Traversal - Iteration Version"))
in_order_iter(node)
print("\n******************************************\n")
print(prompt() + "\n")

print("\n********* Post Order Traversal - Iteration Version ************")
print(prompt("Post Order Traversal - Iteration Version"))
post_order_iter(node)
print("\n******************************************\n")
print(prompt())