From f6bcd000f1005a48fd9e3262059a08745a0d6166 Mon Sep 17 00:00:00 2001
From: Harsh Raj Singhania
 <40535627+HarshRajSinghania@users.noreply.github.com>
Date: Thu, 10 Sep 2026 00:09:40 +0530
Subject: [PATCH] sorts: type double sort for comparable items

---
 sorts/double_sort.py | 98 ++++++++++++++++++++++++--------------------
 tests/test_sorts.py  |  1 +
 2 files changed, 55 insertions(+), 44 deletions(-)

diff --git a/sorts/double_sort.py b/sorts/double_sort.py
index bd5fdca1e63c..20bf2ff9ddd5 100644
--- a/sorts/double_sort.py
+++ b/sorts/double_sort.py
@@ -1,44 +1,54 @@
-from typing import Any
-
-
-def double_sort(collection: list[Any]) -> list[Any]:
-    """This sorting algorithm sorts an array using the principle of bubble sort,
-    but does it both from left to right and right to left.
-    Hence, it's called "Double sort"
-    :param collection: mutable ordered sequence of elements
-    :return: the same collection in ascending order
-    Examples:
-    >>> double_sort([-1 ,-2 ,-3 ,-4 ,-5 ,-6 ,-7])
-    [-7, -6, -5, -4, -3, -2, -1]
-    >>> double_sort([])
-    []
-    >>> double_sort([-1 ,-2 ,-3 ,-4 ,-5 ,-6])
-    [-6, -5, -4, -3, -2, -1]
-    >>> double_sort([-3, 10, 16, -42, 29]) == sorted([-3, 10, 16, -42, 29])
-    True
-    """
-    no_of_elements = len(collection)
-    for _ in range(
-        int(((no_of_elements - 1) / 2) + 1)
-    ):  # we don't need to traverse to end of list as
-        for j in range(no_of_elements - 1):
-            # apply the bubble sort algorithm from left to right (or forwards)
-            if collection[j + 1] < collection[j]:
-                collection[j], collection[j + 1] = collection[j + 1], collection[j]
-            # apply the bubble sort algorithm from right to left (or backwards)
-            if collection[no_of_elements - 1 - j] < collection[no_of_elements - 2 - j]:
-                (
-                    collection[no_of_elements - 1 - j],
-                    collection[no_of_elements - 2 - j],
-                ) = (
-                    collection[no_of_elements - 2 - j],
-                    collection[no_of_elements - 1 - j],
-                )
-    return collection
-
-
-if __name__ == "__main__":
-    # allow the user to input the elements of the list on one line
-    unsorted = [int(x) for x in input("Enter the list to be sorted: ").split() if x]
-    print("the sorted list is")
-    print(f"{double_sort(unsorted) = }")
+
+from typing import Protocol
+
+
+class Comparable(Protocol):
+    def __lt__(self, other: object, /) -> bool: ...
+
+
+def double_sort[T: Comparable](collection: list[T]) -> list[T]:
+    """This sorting algorithm sorts an array using the principle of bubble sort,
+    but does it both from left to right and right to left.
+    Hence, it's called "Double sort"
+    :param collection: mutable ordered sequence of elements
+    :return: the same collection in ascending order
+    Examples:
+    >>> double_sort([-1 ,-2 ,-3 ,-4 ,-5 ,-6 ,-7])
+    [-7, -6, -5, -4, -3, -2, -1]
+    >>> double_sort([])
+    []
+    >>> double_sort([-1 ,-2 ,-3 ,-4 ,-5 ,-6])
+    [-6, -5, -4, -3, -2, -1]
+    >>> double_sort([-3, 10, 16, -42, 29]) == sorted([-3, 10, 16, -42, 29])
+    True
+
+    >>> double_sort(["d", "a", "c", "b"])
+    ['a', 'b', 'c', 'd']
+    >>> double_sort([2.5, -1.0, 0.0])
+    [-1.0, 0.0, 2.5]
+"""
+    no_of_elements = len(collection)
+    for _ in range(
+        int(((no_of_elements - 1) / 2) + 1)
+    ):  # we don't need to traverse to end of list as
+        for j in range(no_of_elements - 1):
+            # apply the bubble sort algorithm from left to right (or forwards)
+            if collection[j + 1] < collection[j]:
+                collection[j], collection[j + 1] = collection[j + 1], collection[j]
+            # apply the bubble sort algorithm from right to left (or backwards)
+            if collection[no_of_elements - 1 - j] < collection[no_of_elements - 2 - j]:
+                (
+                    collection[no_of_elements - 1 - j],
+                    collection[no_of_elements - 2 - j],
+                ) = (
+                    collection[no_of_elements - 2 - j],
+                    collection[no_of_elements - 1 - j],
+                )
+    return collection
+
+
+if __name__ == "__main__":
+    # allow the user to input the elements of the list on one line
+    unsorted = [int(x) for x in input("Enter the list to be sorted: ").split() if x]
+    print("the sorted list is")
+    print(f"{double_sort(unsorted) = }")
diff --git a/tests/test_sorts.py b/tests/test_sorts.py
index caa4b31cac81..8394a96aef80 100644
--- a/tests/test_sorts.py
+++ b/tests/test_sorts.py
@@ -96,6 +96,7 @@ def test_sort_matches_builtin(sort, case):
         bubble_sort_iterative,
         bubble_sort_recursive,
         insertion_sort,
+        double_sort,
     ],
     ids=lambda f: f.__name__,
 )