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145 lines
4.2 KiB
Python
145 lines
4.2 KiB
Python
from __future__ import annotations
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from collections.abc import Iterator
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from typing import Any
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class Node:
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def __init__(self, data: Any):
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self.data: Any = data
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self.next: Node | None = None
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class CircularLinkedList:
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def __init__(self):
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self.head = None
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self.tail = None
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def __iter__(self) -> Iterator[Any]:
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node = self.head
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while self.head:
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yield node.data
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node = node.next
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if node == self.head:
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break
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def __len__(self) -> int:
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return sum(1 for _ in self)
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def __repr__(self):
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return "->".join(str(item) for item in iter(self))
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def insert_tail(self, data: Any) -> None:
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self.insert_nth(len(self), data)
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def insert_head(self, data: Any) -> None:
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self.insert_nth(0, data)
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def insert_nth(self, index: int, data: Any) -> None:
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if index < 0 or index > len(self):
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raise IndexError("list index out of range.")
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new_node = Node(data)
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if self.head is None:
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new_node.next = new_node # first node points itself
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self.tail = self.head = new_node
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elif index == 0: # insert at head
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new_node.next = self.head
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self.head = self.tail.next = new_node
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else:
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temp = self.head
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for _ in range(index - 1):
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temp = temp.next
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new_node.next = temp.next
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temp.next = new_node
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if index == len(self) - 1: # insert at tail
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self.tail = new_node
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def delete_front(self):
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return self.delete_nth(0)
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def delete_tail(self) -> Any:
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return self.delete_nth(len(self) - 1)
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def delete_nth(self, index: int = 0) -> Any:
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if not 0 <= index < len(self):
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raise IndexError("list index out of range.")
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delete_node = self.head
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if self.head == self.tail: # just one node
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self.head = self.tail = None
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elif index == 0: # delete head node
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self.tail.next = self.tail.next.next
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self.head = self.head.next
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else:
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temp = self.head
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for _ in range(index - 1):
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temp = temp.next
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delete_node = temp.next
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temp.next = temp.next.next
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if index == len(self) - 1: # delete at tail
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self.tail = temp
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return delete_node.data
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def is_empty(self) -> bool:
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return len(self) == 0
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def test_circular_linked_list() -> None:
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"""
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>>> test_circular_linked_list()
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"""
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circular_linked_list = CircularLinkedList()
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assert len(circular_linked_list) == 0
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assert circular_linked_list.is_empty() is True
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assert str(circular_linked_list) == ""
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try:
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circular_linked_list.delete_front()
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raise AssertionError # This should not happen
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except IndexError:
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assert True # This should happen
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try:
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circular_linked_list.delete_tail()
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raise AssertionError # This should not happen
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except IndexError:
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assert True # This should happen
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try:
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circular_linked_list.delete_nth(-1)
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raise AssertionError
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except IndexError:
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assert True
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try:
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circular_linked_list.delete_nth(0)
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raise AssertionError
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except IndexError:
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assert True
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assert circular_linked_list.is_empty() is True
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for i in range(5):
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assert len(circular_linked_list) == i
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circular_linked_list.insert_nth(i, i + 1)
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assert str(circular_linked_list) == "->".join(str(i) for i in range(1, 6))
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circular_linked_list.insert_tail(6)
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assert str(circular_linked_list) == "->".join(str(i) for i in range(1, 7))
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circular_linked_list.insert_head(0)
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assert str(circular_linked_list) == "->".join(str(i) for i in range(7))
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assert circular_linked_list.delete_front() == 0
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assert circular_linked_list.delete_tail() == 6
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assert str(circular_linked_list) == "->".join(str(i) for i in range(1, 6))
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assert circular_linked_list.delete_nth(2) == 3
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circular_linked_list.insert_nth(2, 3)
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assert str(circular_linked_list) == "->".join(str(i) for i in range(1, 6))
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assert circular_linked_list.is_empty() is False
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if __name__ == "__main__":
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import doctest
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doctest.testmod()
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