Update adaptive_merge_sort.py

Author: anant-jain01

sorts/adaptive_merge_sort.py

@@ -1,4 +1,4 @@
-def adaptive_merge_sort(sequence: list) -> list:
+    def adaptive_merge_sort(sequence: list) -> list:
     """
     Sorts a list using the Adaptive Merge Sort algorithm.
 
@@ -17,6 +17,7 @@ def adaptive_merge_sort(sequence: list) -> list:
     """
     if len(sequence) < 2:
         return sequence
+    
     aux = sequence[:]
     print(f"Initial sequence: {sequence}")
     adaptive_merge_sort_helper(sequence, aux, 0, len(sequence) - 1)
@@ -40,14 +41,18 @@ def adaptive_merge_sort_helper(array: list, aux: list, low: int, high: int) -> N
     """
     if high <= low:
         return
+    
     mid = (low + high) // 2
     print(f"Sorting: array[{low}:{mid + 1}] and array[{mid + 1}:{high + 1}]")
+    
     adaptive_merge_sort_helper(aux, array, low, mid)
     adaptive_merge_sort_helper(aux, array, mid + 1, high)
+    
     if array[mid] <= array[mid + 1]:
         print(f"Skipping merge as array[{mid}] <= array[{mid + 1}]")
-        array[low : high + 1] = aux[low : high + 1]
+        array[low:high + 1] = aux[low:high + 1]
         return
+    
     merge(array, aux, low, mid, high)
 
 
@@ -60,6 +65,7 @@ def merge(array: list, aux: list, low: int, mid: int, high: int) -> None:
     After merge: [1, 2, 3, 4]
     """
     print(f"Merging: array[{low}:{mid + 1}] and array[{mid + 1}:{high + 1}]")
+    
     i, j = low, mid + 1
     for k in range(low, high + 1):
         if i > mid:
@@ -68,13 +74,19 @@ def merge(array: list, aux: list, low: int, mid: int, high: int) -> None:
         elif j > high:
             aux[k] = array[i]
             i += 1
-        elif array[j] < array[i]:
-            aux[k] = array[j]
-            j += 1
-        else:
+        elif array[i] <= array[j]:  # Keep stable by using <=
             aux[k] = array[i]
             i += 1
-    # Ensure we correctly copy back to the main array
+        else:
+            aux[k] = array[j]
+            j += 1
+    
     for k in range(low, high + 1):
         array[k] = aux[k]
-    print(f"After merge: {aux[low:high + 1]}")
+    
+    print(f"After merge: {array[low:high + 1]}")
+
+
+# Example usage
+if __name__ == "__main__":
+    print(adaptive_merge_sort([4, 3, 1, 2]))