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algorithm/data_structures/binary_tree/binary_tree_node_sum.py
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""" | ||
Sum of all nodes in a binary tree. | ||
Python implementation: | ||
O(n) time complexity - Recurses through :meth:`depth_first_search` | ||
with each element. | ||
O(n) space complexity - At any point in time maximum number of stack | ||
frames that could be in memory is `n` | ||
""" | ||
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from __future__ import annotations | ||
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from collections.abc import Iterator | ||
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class Node: | ||
""" | ||
A Node has a value variable and pointers to Nodes to its left and right. | ||
""" | ||
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def __init__(self, value: int) -> None: | ||
self.value = value | ||
self.left: Node | None = None | ||
self.right: Node | None = None | ||
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class BinaryTreeNodeSum: | ||
r""" | ||
The below tree looks like this | ||
10 | ||
/ \ | ||
5 -3 | ||
/ / \ | ||
12 8 0 | ||
>>> tree = Node(10) | ||
>>> sum(BinaryTreeNodeSum(tree)) | ||
10 | ||
>>> tree.left = Node(5) | ||
>>> sum(BinaryTreeNodeSum(tree)) | ||
15 | ||
>>> tree.right = Node(-3) | ||
>>> sum(BinaryTreeNodeSum(tree)) | ||
12 | ||
>>> tree.left.left = Node(12) | ||
>>> sum(BinaryTreeNodeSum(tree)) | ||
24 | ||
>>> tree.right.left = Node(8) | ||
>>> tree.right.right = Node(0) | ||
>>> sum(BinaryTreeNodeSum(tree)) | ||
32 | ||
""" | ||
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def __init__(self, tree: Node) -> None: | ||
self.tree = tree | ||
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def depth_first_search(self, node: Node | None) -> int: | ||
if node is None: | ||
return 0 | ||
return node.value + ( | ||
self.depth_first_search(node.left) + self.depth_first_search(node.right) | ||
) | ||
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def __iter__(self) -> Iterator[int]: | ||
yield self.depth_first_search(self.tree) | ||
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if __name__ == "__main__": | ||
import doctest | ||
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doctest.testmod() |