Python/data_structures/linked_list/circular_linked_list.py
Tianyi Zheng dfdd78135d
Fix mypy errors in circular_linked_list.py and swap_nodes.py (#9707)
* updating DIRECTORY.md

* Fix mypy errors in circular_linked_list.py

* Fix mypy errors in swap_nodes.py

---------

Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com>
2023-10-04 18:05:00 +02:00

216 lines
6.9 KiB
Python

from __future__ import annotations
from collections.abc import Iterator
from typing import Any
class Node:
def __init__(self, data: Any):
"""
Initialize a new Node with the given data.
Args:
data: The data to be stored in the node.
"""
self.data: Any = data
self.next: Node | None = None # Reference to the next node
class CircularLinkedList:
def __init__(self) -> None:
"""
Initialize an empty Circular Linked List.
"""
self.head: Node | None = None # Reference to the head (first node)
self.tail: Node | None = None # Reference to the tail (last node)
def __iter__(self) -> Iterator[Any]:
"""
Iterate through all nodes in the Circular Linked List yielding their data.
Yields:
The data of each node in the linked list.
"""
node = self.head
while node:
yield node.data
node = node.next
if node == self.head:
break
def __len__(self) -> int:
"""
Get the length (number of nodes) in the Circular Linked List.
"""
return sum(1 for _ in self)
def __repr__(self) -> str:
"""
Generate a string representation of the Circular Linked List.
Returns:
A string of the format "1->2->....->N".
"""
return "->".join(str(item) for item in iter(self))
def insert_tail(self, data: Any) -> None:
"""
Insert a node with the given data at the end of the Circular Linked List.
"""
self.insert_nth(len(self), data)
def insert_head(self, data: Any) -> None:
"""
Insert a node with the given data at the beginning of the Circular Linked List.
"""
self.insert_nth(0, data)
def insert_nth(self, index: int, data: Any) -> None:
"""
Insert the data of the node at the nth pos in the Circular Linked List.
Args:
index: The index at which the data should be inserted.
data: The data to be inserted.
Raises:
IndexError: If the index is out of range.
"""
if index < 0 or index > len(self):
raise IndexError("list index out of range.")
new_node: Node = Node(data)
if self.head is None:
new_node.next = new_node # First node points to itself
self.tail = self.head = new_node
elif index == 0: # Insert at the head
new_node.next = self.head
assert self.tail is not None # List is not empty, tail exists
self.head = self.tail.next = new_node
else:
temp: Node | None = self.head
for _ in range(index - 1):
assert temp is not None
temp = temp.next
assert temp is not None
new_node.next = temp.next
temp.next = new_node
if index == len(self) - 1: # Insert at the tail
self.tail = new_node
def delete_front(self) -> Any:
"""
Delete and return the data of the node at the front of the Circular Linked List.
Raises:
IndexError: If the list is empty.
"""
return self.delete_nth(0)
def delete_tail(self) -> Any:
"""
Delete and return the data of the node at the end of the Circular Linked List.
Returns:
Any: The data of the deleted node.
Raises:
IndexError: If the index is out of range.
"""
return self.delete_nth(len(self) - 1)
def delete_nth(self, index: int = 0) -> Any:
"""
Delete and return the data of the node at the nth pos in Circular Linked List.
Args:
index (int): The index of the node to be deleted. Defaults to 0.
Returns:
Any: The data of the deleted node.
Raises:
IndexError: If the index is out of range.
"""
if not 0 <= index < len(self):
raise IndexError("list index out of range.")
assert self.head is not None and self.tail is not None
delete_node: Node = self.head
if self.head == self.tail: # Just one node
self.head = self.tail = None
elif index == 0: # Delete head node
assert self.tail.next is not None
self.tail.next = self.tail.next.next
self.head = self.head.next
else:
temp: Node | None = self.head
for _ in range(index - 1):
assert temp is not None
temp = temp.next
assert temp is not None and temp.next is not None
delete_node = temp.next
temp.next = temp.next.next
if index == len(self) - 1: # Delete at tail
self.tail = temp
return delete_node.data
def is_empty(self) -> bool:
"""
Check if the Circular Linked List is empty.
Returns:
bool: True if the list is empty, False otherwise.
"""
return len(self) == 0
def test_circular_linked_list() -> None:
"""
Test cases for the CircularLinkedList class.
>>> test_circular_linked_list()
"""
circular_linked_list = CircularLinkedList()
assert len(circular_linked_list) == 0
assert circular_linked_list.is_empty() is True
assert str(circular_linked_list) == ""
try:
circular_linked_list.delete_front()
raise AssertionError # This should not happen
except IndexError:
assert True # This should happen
try:
circular_linked_list.delete_tail()
raise AssertionError # This should not happen
except IndexError:
assert True # This should happen
try:
circular_linked_list.delete_nth(-1)
raise AssertionError
except IndexError:
assert True
try:
circular_linked_list.delete_nth(0)
raise AssertionError
except IndexError:
assert True
assert circular_linked_list.is_empty() is True
for i in range(5):
assert len(circular_linked_list) == i
circular_linked_list.insert_nth(i, i + 1)
assert str(circular_linked_list) == "->".join(str(i) for i in range(1, 6))
circular_linked_list.insert_tail(6)
assert str(circular_linked_list) == "->".join(str(i) for i in range(1, 7))
circular_linked_list.insert_head(0)
assert str(circular_linked_list) == "->".join(str(i) for i in range(7))
assert circular_linked_list.delete_front() == 0
assert circular_linked_list.delete_tail() == 6
assert str(circular_linked_list) == "->".join(str(i) for i in range(1, 6))
assert circular_linked_list.delete_nth(2) == 3
circular_linked_list.insert_nth(2, 3)
assert str(circular_linked_list) == "->".join(str(i) for i in range(1, 6))
assert circular_linked_list.is_empty() is False
if __name__ == "__main__":
import doctest
doctest.testmod()