Create adaptive_merge_sort.py

sorts/adaptive_merge_sort.py

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+"""
+Adaptive Merge Sort implementation.
+https://en.wikipedia.org/wiki/Merge_sort
+"""
+
+
+def adaptive_merge_sort(sequence: list) -> list:
+    """
+    >>> adaptive_merge_sort([12, 11, 13, 5, 6, 7])
+    [5, 6, 7, 11, 12, 13]
+
+    >>> adaptive_merge_sort([4, 3, 2, 1])
+    [1, 2, 3, 4]
+
+    >>> adaptive_merge_sort(["apple", "zebra", "mango", "banana"])
+    ['apple', 'banana', 'mango', 'zebra']
+    """
+    if len(sequence) < 2:
+        return sequence
+
+    aux = sequence[:]
+    adaptive_merge_sort_recursive(sequence, aux, 0, len(sequence) - 1)
+    return sequence
+
+
+def adaptive_merge_sort_recursive(arr: list, aux: list, low: int, high: int) -> None:
+    if high <= low:
+        return
+
+    mid = (low + high) // 2
+    adaptive_merge_sort_recursive(aux, arr, low, mid)
+    adaptive_merge_sort_recursive(aux, arr, mid + 1, high)
+
+    if arr[mid] <= arr[mid + 1]:
+        arr[low : high + 1] = aux[low : high + 1]
+        return
+
+    merge(arr, aux, low, mid, high)
+
+
+def merge(arr: list, aux: list, low: int, mid: int, high: int) -> None:
+    i, j = low, mid + 1
+
+    for k in range(low, high + 1):
+        if i > mid:
+            aux[k] = arr[j]
+            j += 1
+        elif j > high:
+            aux[k] = arr[i]
+            i += 1
+        elif arr[j] < arr[i]:
+            aux[k] = arr[j]
+            j += 1
+        else:
+            aux[k] = arr[i]
+            i += 1
+
+
+if __name__ == "__main__":
+    assert adaptive_merge_sort([12, 11, 13, 5, 6, 7]) == [5, 6, 7, 11, 12, 13]
+    assert adaptive_merge_sort([4, 3, 2, 1]) == [1, 2, 3, 4]
+    assert adaptive_merge_sort(["apple", "zebra", "mango", "banana"]) == [
+        "apple",
+        "banana",
+        "mango",
+        "zebra",
+    ]