Python/data_structures/binary_tree/binary_tree_path_sum.py
Caeden Perelli-Harris 25757e697c
Binary tree path sum ()
* feat: Implement binary tree path sum ()

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* Update data_structures/binary_tree/binary_tree_path_sum.py

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

* refactor: Rename `dfs` to `depth_first_search`

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Christian Clauss <cclauss@me.com>
2022-10-27 23:03:01 +02:00

89 lines
2.0 KiB
Python

"""
Given the root of a binary tree and an integer target,
find the number of paths where the sum of the values
along the path equals target.
Leetcode reference: https://leetcode.com/problems/path-sum-iii/
"""
from __future__ import annotations
class Node:
"""
A Node has value variable and pointers to Nodes to its left and right.
"""
def __init__(self, value: int) -> None:
self.value = value
self.left: Node | None = None
self.right: Node | None = None
class BinaryTreePathSum:
r"""
The below tree looks like this
10
/ \
5 -3
/ \ \
3 2 11
/ \ \
3 -2 1
>>> tree = Node(10)
>>> tree.left = Node(5)
>>> tree.right = Node(-3)
>>> tree.left.left = Node(3)
>>> tree.left.right = Node(2)
>>> tree.right.right = Node(11)
>>> tree.left.left.left = Node(3)
>>> tree.left.left.right = Node(-2)
>>> tree.left.right.right = Node(1)
>>> BinaryTreePathSum().path_sum(tree, 8)
3
>>> BinaryTreePathSum().path_sum(tree, 7)
2
>>> tree.right.right = Node(10)
>>> BinaryTreePathSum().path_sum(tree, 8)
2
"""
target: int
def __init__(self) -> None:
self.paths = 0
def depth_first_search(self, node: Node | None, path_sum: int) -> None:
if node is None:
return
if path_sum == self.target:
self.paths += 1
if node.left:
self.depth_first_search(node.left, path_sum + node.left.value)
if node.right:
self.depth_first_search(node.right, path_sum + node.right.value)
def path_sum(self, node: Node | None, target: int | None = None) -> int:
if node is None:
return 0
if target is not None:
self.target = target
self.depth_first_search(node, node.value)
self.path_sum(node.left)
self.path_sum(node.right)
return self.paths
if __name__ == "__main__":
import doctest
doctest.testmod()