Python/data_structures/binary_tree/diff_views_of_binary_tree.py

211 lines
4.7 KiB
Python
Raw Normal View History

r"""
Problem: Given root of a binary tree, return the:
1. binary-tree-right-side-view
2. binary-tree-left-side-view
3. binary-tree-top-side-view
4. binary-tree-bottom-side-view
"""
from __future__ import annotations
from collections import defaultdict
from dataclasses import dataclass
@dataclass
class TreeNode:
val: int
left: TreeNode | None = None
right: TreeNode | None = None
def make_tree() -> TreeNode:
"""
>>> make_tree().val
3
"""
return TreeNode(3, TreeNode(9), TreeNode(20, TreeNode(15), TreeNode(7)))
def binary_tree_right_side_view(root: TreeNode) -> list[int]:
r"""
Function returns the right side view of binary tree.
3 <- 3
/ \
9 20 <- 20
/ \
15 7 <- 7
>>> binary_tree_right_side_view(make_tree())
[3, 20, 7]
>>> binary_tree_right_side_view(None)
[]
"""
def depth_first_search(
root: TreeNode | None, depth: int, right_view: list[int]
) -> None:
"""
A depth first search preorder traversal to append the values at
right side of tree.
"""
if not root:
return
if depth == len(right_view):
right_view.append(root.val)
depth_first_search(root.right, depth + 1, right_view)
depth_first_search(root.left, depth + 1, right_view)
right_view: list = []
if not root:
return right_view
depth_first_search(root, 0, right_view)
return right_view
def binary_tree_left_side_view(root: TreeNode) -> list[int]:
r"""
Function returns the left side view of binary tree.
3 -> 3
/ \
9 -> 9 20
/ \
15 -> 15 7
>>> binary_tree_left_side_view(make_tree())
[3, 9, 15]
>>> binary_tree_left_side_view(None)
[]
"""
def depth_first_search(
root: TreeNode | None, depth: int, left_view: list[int]
) -> None:
"""
A depth first search preorder traversal to append the values
at left side of tree.
"""
if not root:
return
if depth == len(left_view):
left_view.append(root.val)
depth_first_search(root.left, depth + 1, left_view)
depth_first_search(root.right, depth + 1, left_view)
left_view: list = []
if not root:
return left_view
depth_first_search(root, 0, left_view)
return left_view
def binary_tree_top_side_view(root: TreeNode) -> list[int]:
r"""
Function returns the top side view of binary tree.
9 3 20 7
3
/ \
9 20
/ \
15 7
>>> binary_tree_top_side_view(make_tree())
[9, 3, 20, 7]
>>> binary_tree_top_side_view(None)
[]
"""
def breadth_first_search(root: TreeNode, top_view: list[int]) -> None:
"""
A breadth first search traversal with defaultdict ds to append
the values of tree from top view
"""
queue = [(root, 0)]
lookup = defaultdict(list)
while queue:
first = queue.pop(0)
node, hd = first
lookup[hd].append(node.val)
if node.left:
queue.append((node.left, hd - 1))
if node.right:
queue.append((node.right, hd + 1))
for pair in sorted(lookup.items(), key=lambda each: each[0]):
top_view.append(pair[1][0])
top_view: list = []
if not root:
return top_view
breadth_first_search(root, top_view)
return top_view
def binary_tree_bottom_side_view(root: TreeNode) -> list[int]:
r"""
Function returns the bottom side view of binary tree
3
/ \
9 20
/ \
15 7
9 15 20 7
>>> binary_tree_bottom_side_view(make_tree())
[9, 15, 20, 7]
>>> binary_tree_bottom_side_view(None)
[]
"""
from collections import defaultdict
def breadth_first_search(root: TreeNode, bottom_view: list[int]) -> None:
"""
A breadth first search traversal with defaultdict ds to append
the values of tree from bottom view
"""
queue = [(root, 0)]
lookup = defaultdict(list)
while queue:
first = queue.pop(0)
node, hd = first
lookup[hd].append(node.val)
if node.left:
queue.append((node.left, hd - 1))
if node.right:
queue.append((node.right, hd + 1))
for pair in sorted(lookup.items(), key=lambda each: each[0]):
bottom_view.append(pair[1][-1])
bottom_view: list = []
if not root:
return bottom_view
breadth_first_search(root, bottom_view)
return bottom_view
if __name__ == "__main__":
import doctest
doctest.testmod()