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sorts: make heap sort support comparable items #15291

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Merged
cclauss merged 2 commits into from
Sep 12, 2026
Merged

sorts: make heap sort support comparable items #15291

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90479cf
sorts: make heap sort support comparable items
Ashwin121425-R Sep 12, 2026
301b96a
style: remove unnecessary blank lines from heap sort
Ashwin121425-R Sep 12, 2026
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32 changes: 25 additions & 7 deletions sorts/heap_sort.py
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Original file line number Diff line number Diff line change
Expand Up @@ -2,10 +2,16 @@
A pure Python implementation of the heap sort algorithm.
"""

from typing import Protocol

def heapify(unsorted: list[int], index: int, heap_size: int) -> None:

class Comparable(Protocol):
def __lt__(self, other: object, /) -> bool: ...


def heapify[T: Comparable](unsorted: list[T], index: int, heap_size: int) -> None:
"""
:param unsorted: unsorted list containing integers numbers
:param unsorted: unsorted list containing comparable items
:param index: index
:param heap_size: size of the heap
:return: None
Expand All @@ -20,22 +26,23 @@ def heapify(unsorted: list[int], index: int, heap_size: int) -> None:
largest = index
left_index = 2 * index + 1
right_index = 2 * index + 2
if left_index < heap_size and unsorted[left_index] > unsorted[largest]:

if left_index < heap_size and unsorted[largest] < unsorted[left_index]:
largest = left_index

if right_index < heap_size and unsorted[right_index] > unsorted[largest]:
if right_index < heap_size and unsorted[largest] < unsorted[right_index]:
largest = right_index

if largest != index:
unsorted[largest], unsorted[index] = (unsorted[index], unsorted[largest])
heapify(unsorted, largest, heap_size)


def heap_sort(unsorted: list[int]) -> list[int]:
def heap_sort[T: Comparable](unsorted: list[T]) -> list[T]:
"""
A pure Python implementation of the heap sort algorithm
A pure Python implementation of the heap sort algorithm.

:param collection: a mutable ordered collection of heterogeneous comparable items
:param unsorted: a mutable collection of comparable items
:return: the same collection ordered by ascending

Examples:
Expand All @@ -47,13 +54,24 @@ def heap_sort(unsorted: list[int]) -> list[int]:
[-45, -5, -2]
>>> heap_sort([3, 7, 9, 28, 123, -5, 8, -30, -200, 0, 4])
[-200, -30, -5, 0, 3, 4, 7, 8, 9, 28, 123]
>>> heap_sort(["banana", "apple", "cherry"])
['apple', 'banana', 'cherry']
>>> heap_sort([3.14, 1.5, 2.7])
[1.5, 2.7, 3.14]
>>> heap_sort([1, "two"]) # doctest: +ELLIPSIS
Traceback (most recent call last):
...
TypeError: ...
"""
n = len(unsorted)

@cclauss cclauss Sep 12, 2026

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Adding these three blank lines is unnecessary. Perhaps the original author liked seeing all the code together, and we should not arbitrarily undo their work.

for i in range(n // 2 - 1, -1, -1):
heapify(unsorted, i, n)

for i in range(n - 1, 0, -1):
unsorted[0], unsorted[i] = unsorted[i], unsorted[0]
heapify(unsorted, 0, i)

return unsorted


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