Python/data_structures/linked_list/merge_two_lists.py
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Python

"""
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
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_node: Node | None
class SortedLinkedList:
def __init__(self, ints: Iterable[int]) -> None:
self.head: Node | None = None
for i in sorted(ints, reverse=True):
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_node
def __len__(self) -> int:
"""
>>> for i in range(3):
... len(SortedLinkedList(range(i))) == i
True
True
True
>>> len(SortedLinkedList(test_data_odd))
8
"""
return sum(1 for _ in 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)))