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25757e697c
* feat: Implement binary tree path sum (#7135) * [pre-commit.ci] auto fixes from pre-commit.com hooks for more information, see https://pre-commit.ci * 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>
89 lines
2.0 KiB
Python
89 lines
2.0 KiB
Python
"""
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Given the root of a binary tree and an integer target,
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find the number of paths where the sum of the values
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along the path equals target.
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Leetcode reference: https://leetcode.com/problems/path-sum-iii/
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"""
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from __future__ import annotations
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class Node:
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"""
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A Node has value variable and pointers to Nodes to its left and right.
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"""
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def __init__(self, value: int) -> None:
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self.value = value
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self.left: Node | None = None
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self.right: Node | None = None
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class BinaryTreePathSum:
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r"""
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The below tree looks like this
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10
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/ \
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5 -3
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/ \ \
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3 2 11
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/ \ \
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3 -2 1
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>>> tree = Node(10)
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>>> tree.left = Node(5)
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>>> tree.right = Node(-3)
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>>> tree.left.left = Node(3)
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>>> tree.left.right = Node(2)
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>>> tree.right.right = Node(11)
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>>> tree.left.left.left = Node(3)
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>>> tree.left.left.right = Node(-2)
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>>> tree.left.right.right = Node(1)
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>>> BinaryTreePathSum().path_sum(tree, 8)
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3
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>>> BinaryTreePathSum().path_sum(tree, 7)
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2
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>>> tree.right.right = Node(10)
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>>> BinaryTreePathSum().path_sum(tree, 8)
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2
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"""
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target: int
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def __init__(self) -> None:
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self.paths = 0
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def depth_first_search(self, node: Node | None, path_sum: int) -> None:
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if node is None:
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return
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if path_sum == self.target:
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self.paths += 1
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if node.left:
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self.depth_first_search(node.left, path_sum + node.left.value)
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if node.right:
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self.depth_first_search(node.right, path_sum + node.right.value)
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def path_sum(self, node: Node | None, target: int | None = None) -> int:
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if node is None:
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return 0
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if target is not None:
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self.target = target
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self.depth_first_search(node, node.value)
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self.path_sum(node.left)
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self.path_sum(node.right)
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return self.paths
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if __name__ == "__main__":
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import doctest
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doctest.testmod()
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