From 860d4f547bcfbe96b5c1e1b507124b13c0dc7399 Mon Sep 17 00:00:00 2001 From: Maliha Date: Thu, 3 Dec 2020 07:02:48 -0800 Subject: [PATCH] Create merge_two_lists.py that implements merging of two sorted linked lists (#3874) * Create merge_two_lists.py that implements merging of two sorted linked lists * Update merge_two_lists.py Fixed formatting errors * Fixed trailing whitespace * Change name of function to def __str__() * updating DIRECTORY.md * Imported classes from singly_linked_list.py * Update merge_two_lists.py * Update merge_two_lists.py Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com> Co-authored-by: Christian Clauss --- DIRECTORY.md | 1 + .../linked_list/merge_two_lists.py | 83 +++++++++++++++++++ 2 files changed, 84 insertions(+) create mode 100644 data_structures/linked_list/merge_two_lists.py diff --git a/DIRECTORY.md b/DIRECTORY.md index 2307685f1..c9c3a09eb 100644 --- a/DIRECTORY.md +++ b/DIRECTORY.md @@ -153,6 +153,7 @@ * [From Sequence](https://github.com/TheAlgorithms/Python/blob/master/data_structures/linked_list/from_sequence.py) * [Has Loop](https://github.com/TheAlgorithms/Python/blob/master/data_structures/linked_list/has_loop.py) * [Is Palindrome](https://github.com/TheAlgorithms/Python/blob/master/data_structures/linked_list/is_palindrome.py) + * [Merge Two Lists](https://github.com/TheAlgorithms/Python/blob/master/data_structures/linked_list/merge_two_lists.py) * [Middle Element Of Linked List](https://github.com/TheAlgorithms/Python/blob/master/data_structures/linked_list/middle_element_of_linked_list.py) * [Print Reverse](https://github.com/TheAlgorithms/Python/blob/master/data_structures/linked_list/print_reverse.py) * [Singly Linked List](https://github.com/TheAlgorithms/Python/blob/master/data_structures/linked_list/singly_linked_list.py) diff --git a/data_structures/linked_list/merge_two_lists.py b/data_structures/linked_list/merge_two_lists.py new file mode 100644 index 000000000..96ec6b8ab --- /dev/null +++ b/data_structures/linked_list/merge_two_lists.py @@ -0,0 +1,83 @@ +""" +Algorithm that merges two sorted linked lists into one sorted linked list. +""" +from __future__ import annotations + +from collections.abc import Iterable, Iterator +from dataclasses import dataclass +from typing import Optional + +test_data_odd = (3, 9, -11, 0, 7, 5, 1, -1) +test_data_even = (4, 6, 2, 0, 8, 10, 3, -2) + + +@dataclass +class Node: + data: int + next: Optional[Node] + + +class SortedLinkedList: + def __init__(self, ints: Iterable[int]) -> None: + self.head: Optional[Node] = None + for i in reversed(sorted(ints)): + self.head = Node(i, self.head) + + def __iter__(self) -> Iterator[int]: + """ + >>> tuple(SortedLinkedList(test_data_odd)) == tuple(sorted(test_data_odd)) + True + >>> tuple(SortedLinkedList(test_data_even)) == tuple(sorted(test_data_even)) + True + """ + node = self.head + while node: + yield node.data + node = node.next + + def __len__(self) -> int: + """ + >>> for i in range(3): + ... len(SortedLinkedList(range(i))) == i + True + True + True + >>> len(SortedLinkedList(test_data_odd)) + 8 + """ + return len(tuple(iter(self))) + + def __str__(self) -> str: + """ + >>> str(SortedLinkedList([])) + '' + >>> str(SortedLinkedList(test_data_odd)) + '-11 -> -1 -> 0 -> 1 -> 3 -> 5 -> 7 -> 9' + >>> str(SortedLinkedList(test_data_even)) + '-2 -> 0 -> 2 -> 3 -> 4 -> 6 -> 8 -> 10' + """ + return " -> ".join([str(node) for node in self]) + + +def merge_lists( + sll_one: SortedLinkedList, sll_two: SortedLinkedList +) -> SortedLinkedList: + """ + >>> SSL = SortedLinkedList + >>> merged = merge_lists(SSL(test_data_odd), SSL(test_data_even)) + >>> len(merged) + 16 + >>> str(merged) + '-11 -> -2 -> -1 -> 0 -> 0 -> 1 -> 2 -> 3 -> 3 -> 4 -> 5 -> 6 -> 7 -> 8 -> 9 -> 10' + >>> list(merged) == list(sorted(test_data_odd + test_data_even)) + True + """ + return SortedLinkedList(list(sll_one) + list(sll_two)) + + +if __name__ == "__main__": + import doctest + + doctest.testmod() + SSL = SortedLinkedList + print(merge_lists(SSL(test_data_odd), SSL(test_data_even)))