added rotate_array.py (TheAlgorithms#13336)

* added rotate_array.py * [pre-commit.ci] auto fixes from pre-commit.com hooks for more information, see https://pre-commit.ci * fixed issues * [pre-commit.ci] auto fixes from pre-commit.com hooks for more information, see https://pre-commit.ci * fixed reverse issue * added doctests * [pre-commit.ci] auto fixes from pre-commit.com hooks for more information, see https://pre-commit.ci * changed k to steps for a descriptive name * fixed non-pep --------- Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

Author: jenyyy4

data_structures/arrays/rotate_array.py

@@ -0,0 +1,80 @@
+def rotate_array(arr: list[int], steps: int) -> list[int]:
+ """
+ Rotates a list to the right by steps positions.
+
+ Parameters:
+ arr (List[int]): The list of integers to rotate.
+ steps (int): Number of positions to rotate. Can be negative for left rotation.
+
+ Returns:
+ List[int]: Rotated list.
+
+ Examples:
+ >>> rotate_array([1, 2, 3, 4, 5], 2)
+ [4, 5, 1, 2, 3]
+ >>> rotate_array([1, 2, 3, 4, 5], -2)
+ [3, 4, 5, 1, 2]
+ >>> rotate_array([1, 2, 3, 4, 5], 7)
+ [4, 5, 1, 2, 3]
+ >>> rotate_array([], 3)
+ []
+ """
+
+ n = len(arr)
+ if n == 0:
+ return arr
+
+ steps = steps % n
+
+ if steps < 0:
+ steps += n
+
+ def reverse(start: int, end: int) -> None:
+ """
+ Reverses a portion of the list in place from index start to end.
+
+ Parameters:
+ start (int): Starting index of the portion to reverse.
+ end (int): Ending index of the portion to reverse.
+
+ Returns:
+ None
+
+ Examples:
+ >>> example = [1, 2, 3, 4, 5]
+ >>> def reverse_test(arr, start, end):
+ ... while start < end:
+ ... arr[start], arr[end] = arr[end], arr[start]
+ ... start += 1
+ ... end -= 1
+ >>> reverse_test(example, 0, 2)
+ >>> example
+ [3, 2, 1, 4, 5]
+ >>> reverse_test(example, 2, 4)
+ >>> example
+ [3, 2, 5, 4, 1]
+ """
+
+ while start < end:
+ arr[start], arr[end] = arr[end], arr[start]
+ start += 1
+ end -= 1
+
+ reverse(0, n - 1)
+ reverse(0, steps - 1)
+ reverse(steps, n - 1)
+
+ return arr
+
+
+if __name__ == "__main__":
+ examples = [
+ ([1, 2, 3, 4, 5], 2),
+ ([1, 2, 3, 4, 5], -2),
+ ([1, 2, 3, 4, 5], 7),
+ ([], 3),
+ ]
+
+ for arr, steps in examples:
+ rotated = rotate_array(arr.copy(), steps)
+ print(f"Rotate {arr} by {steps}: {rotated}")