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1ae5abfc3c
* Replace typing.optional with new annotations syntax
* updating DIRECTORY.md
Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com>
63 lines
1.7 KiB
Python
63 lines
1.7 KiB
Python
from __future__ import annotations
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from typing import Any
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class ContainsLoopError(Exception):
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pass
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class Node:
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def __init__(self, data: Any) -> None:
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self.data: Any = data
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self.next_node: Node | None = None
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def __iter__(self):
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node = self
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visited = []
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while node:
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if node in visited:
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raise ContainsLoopError
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visited.append(node)
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yield node.data
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node = node.next_node
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@property
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def has_loop(self) -> bool:
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"""
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A loop is when the exact same Node appears more than once in a linked list.
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>>> root_node = Node(1)
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>>> root_node.next_node = Node(2)
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>>> root_node.next_node.next_node = Node(3)
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>>> root_node.next_node.next_node.next_node = Node(4)
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>>> root_node.has_loop
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False
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>>> root_node.next_node.next_node.next_node = root_node.next_node
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>>> root_node.has_loop
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True
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"""
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try:
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list(self)
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return False
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except ContainsLoopError:
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return True
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if __name__ == "__main__":
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root_node = Node(1)
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root_node.next_node = Node(2)
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root_node.next_node.next_node = Node(3)
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root_node.next_node.next_node.next_node = Node(4)
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print(root_node.has_loop) # False
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root_node.next_node.next_node.next_node = root_node.next_node
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print(root_node.has_loop) # True
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root_node = Node(5)
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root_node.next_node = Node(6)
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root_node.next_node.next_node = Node(5)
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root_node.next_node.next_node.next_node = Node(6)
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print(root_node.has_loop) # False
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root_node = Node(1)
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print(root_node.has_loop) # False
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