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Fix/tree sort iterable type hint #14701

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Fix/tree sort iterable type hint #14701

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161a738
sorts/tree_sort: use Iterable type hint and enable range doctest
DrishtiTripathi2230 May 19, 2026
9022e8a
[pre-commit.ci] auto fixes from pre-commit.com hooks
pre-commit-ci[bot] May 20, 2026
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9 changes: 4 additions & 5 deletions sorts/tree_sort.py
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Original file line number Diff line number Diff line change
@@ -1,12 +1,11 @@
"""
Tree_sort algorithm.

Build a Binary Search Tree and then iterate thru it to get a sorted list.
"""

from __future__ import annotations

from collections.abc import Iterator
from collections.abc import Iterable, Iterator
from dataclasses import dataclass


Expand Down Expand Up @@ -39,7 +38,7 @@ def insert(self, val: int) -> None:
self.right.insert(val)


def tree_sort(arr: list[int]) -> tuple[int, ...]:
def tree_sort(arr: Iterable[int]) -> tuple[int, ...]:
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@diusazzad diusazzad May 24, 2026

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Hey @DrishtiTripathi2230! Thanks for taking the time to improve the type hints! 🚀

Changing the type hint to Iterable[int] is a great idea conceptually. However, it introduces a subtle bug. Since Iterable includes generators, passing a generator will cause the code to crash because:

  1. len(arr) will raise a TypeError (generators have no len()).
  2. arr[0] and arr[1:] will also raise a TypeError (generators are not subscriptable).

To fix this and fully support any Iterable, we can convert the iterable into an iterator using iter(). Here is a suggested fix for the logic inside the function:

def tree_sort(arr: Iterable[int]) -> tuple[int, ...]:
    # ... docstrings ...
    iterator = iter(arr)
    try:
        first = next(iterator)
    except StopIteration:
        return ()
        
    root = Node(first)
    for item in iterator:
        root.insert(item)
    return tuple(root)

"""
>>> tree_sort([])
()
Expand All @@ -54,8 +53,8 @@ def tree_sort(arr: list[int]) -> tuple[int, ...]:
>>> tree_sort([5, 6, 1, -1, 4, 37, 2, 7])
(-1, 1, 2, 4, 5, 6, 7, 37)

# >>> tree_sort(range(10, -10, -1)) == tuple(sorted(range(10, -10, -1)))
# True
>>> tree_sort(range(10, -10, -1)) == tuple(sorted(range(10, -10, -1)))
True
"""
if len(arr) == 0:
return tuple(arr)
Expand Down