From 24714510b18d5c127d4da6d729d40703be71c87a Mon Sep 17 00:00:00 2001
From: Ferbiya Peter <167544996+FerbiyaP@users.noreply.github.com>
Date: Wed, 16 Sep 2026 18:40:24 +0530
Subject: [PATCH] Refactor adaptive_merge_sort for type safety with Protocol

---
 sorts/adaptive_merge_sort.py | 24 +++++++++++++++++++-----
 1 file changed, 19 insertions(+), 5 deletions(-)

diff --git a/sorts/adaptive_merge_sort.py b/sorts/adaptive_merge_sort.py
index 157532aab98d..45d6d07f4a01 100644
--- a/sorts/adaptive_merge_sort.py
+++ b/sorts/adaptive_merge_sort.py
@@ -1,4 +1,11 @@
-def adaptive_merge_sort(sequence: list) -> list:
+from typing import Protocol
+
+
+class Comparable(Protocol):
+    def __lt__(self, other: object, /) -> bool: ...
+
+
+def adaptive_merge_sort[T: Comparable](sequence: list[T]) -> list[T]:
     if len(sequence) < 2:
         return sequence
 
@@ -9,7 +16,9 @@ def adaptive_merge_sort(sequence: list) -> list:
     return sequence
 
 
-def adaptive_merge_sort_helper(array: list, aux: list, low: int, high: int) -> None:
+def adaptive_merge_sort_helper[T: Comparable](
+    array: list[T], aux: list[T], low: int, high: int
+) -> None:
     if high <= low:
         return
 
@@ -19,7 +28,7 @@ def adaptive_merge_sort_helper(array: list, aux: list, low: int, high: int) -> N
     adaptive_merge_sort_helper(aux, array, low, mid)
     adaptive_merge_sort_helper(aux, array, mid + 1, high)
 
-    if array[mid] <= array[mid + 1]:
+    if not array[mid + 1] < array[mid]:
         print(f"Skipping merge as array[{mid}] <= array[{mid + 1}]")
         array[low : high + 1] = aux[low : high + 1]
         return
@@ -27,7 +36,9 @@ def adaptive_merge_sort_helper(array: list, aux: list, low: int, high: int) -> N
     merge(array, aux, low, mid, high)
 
 
-def merge(array: list, aux: list, low: int, mid: int, high: int) -> None:
+def merge[T: Comparable](
+    array: list[T], aux: list[T], low: int, mid: int, high: int
+) -> None:
     print(f"Merging: array[{low}:{mid + 1}] and array[{mid + 1}:{high + 1}]")
 
     i, j = low, mid + 1
@@ -39,7 +50,7 @@ def merge(array: list, aux: list, low: int, mid: int, high: int) -> None:
             else:
                 aux[k] = array[i]
                 i += 1
-        elif array[i] <= array[j]:
+        elif not array[j] < array[i]:
             aux[k] = array[i]
             i += 1
         else:
@@ -55,3 +66,6 @@ def merge(array: list, aux: list, low: int, mid: int, high: int) -> None:
 # Example usage
 if __name__ == "__main__":
     print(adaptive_merge_sort([4, 3, 1, 2]))
+# Example usage
+if __name__ == "__main__":
+    print(adaptive_merge_sort([4, 3, 1, 2]))