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5869fda742
* print reverse: A LinkedList with a tail pointer
* updating DIRECTORY.md
---------
Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com>
127 lines
3.5 KiB
Python
127 lines
3.5 KiB
Python
from __future__ import annotations
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from collections.abc import Iterable, Iterator
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from dataclasses import dataclass
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@dataclass
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class Node:
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data: int
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next_node: Node | None = None
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class LinkedList:
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"""A class to represent a Linked List.
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Use a tail pointer to speed up the append() operation.
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"""
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def __init__(self) -> None:
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"""Initialize a LinkedList with the head node set to None.
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>>> linked_list = LinkedList()
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>>> (linked_list.head, linked_list.tail)
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(None, None)
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"""
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self.head: Node | None = None
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self.tail: Node | None = None # Speeds up the append() operation
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def __iter__(self) -> Iterator[int]:
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"""Iterate the LinkedList yielding each Node's data.
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>>> linked_list = LinkedList()
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>>> items = (1, 2, 3, 4, 5)
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>>> linked_list.extend(items)
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>>> tuple(linked_list) == items
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True
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"""
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node = self.head
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while node:
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yield node.data
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node = node.next_node
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def __repr__(self) -> str:
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"""Returns a string representation of the LinkedList.
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>>> linked_list = LinkedList()
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>>> str(linked_list)
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''
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>>> linked_list.append(1)
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>>> str(linked_list)
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'1'
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>>> linked_list.extend([2, 3, 4, 5])
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>>> str(linked_list)
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'1 -> 2 -> 3 -> 4 -> 5'
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"""
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return " -> ".join([str(data) for data in self])
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def append(self, data: int) -> None:
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"""Appends a new node with the given data to the end of the LinkedList.
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>>> linked_list = LinkedList()
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>>> str(linked_list)
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''
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>>> linked_list.append(1)
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>>> str(linked_list)
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'1'
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>>> linked_list.append(2)
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>>> str(linked_list)
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'1 -> 2'
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"""
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if self.tail:
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self.tail.next_node = self.tail = Node(data)
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else:
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self.head = self.tail = Node(data)
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def extend(self, items: Iterable[int]) -> None:
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"""Appends each item to the end of the LinkedList.
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>>> linked_list = LinkedList()
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>>> linked_list.extend([])
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>>> str(linked_list)
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''
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>>> linked_list.extend([1, 2])
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>>> str(linked_list)
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'1 -> 2'
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>>> linked_list.extend([3,4])
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>>> str(linked_list)
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'1 -> 2 -> 3 -> 4'
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"""
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for item in items:
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self.append(item)
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def make_linked_list(elements_list: Iterable[int]) -> LinkedList:
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"""Creates a Linked List from the elements of the given sequence
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(list/tuple) and returns the head of the Linked List.
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>>> make_linked_list([])
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Traceback (most recent call last):
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...
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Exception: The Elements List is empty
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>>> make_linked_list([7])
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7
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>>> make_linked_list(['abc'])
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abc
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>>> make_linked_list([7, 25])
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7 -> 25
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"""
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if not elements_list:
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raise Exception("The Elements List is empty")
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linked_list = LinkedList()
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linked_list.extend(elements_list)
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return linked_list
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def in_reverse(linked_list: LinkedList) -> str:
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"""Prints the elements of the given Linked List in reverse order
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>>> in_reverse(LinkedList())
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''
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>>> in_reverse(make_linked_list([69, 88, 73]))
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'73 <- 88 <- 69'
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"""
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return " <- ".join(str(line) for line in reversed(tuple(linked_list)))
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if __name__ == "__main__":
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from doctest import testmod
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testmod()
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linked_list = make_linked_list((14, 52, 14, 12, 43))
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print(f"Linked List: {linked_list}")
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print(f"Reverse List: {in_reverse(linked_list)}")
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