Added rotate_array.py

Author: davidw1281

data_structures/arrays/rotate_array.py

@@ -0,0 +1,130 @@
+"""
+Given an integer array nums and a non-negative integer k, rotate
+nums to the right by k places.
+
+LeetCode Link: https://leetcode.com/problems/rotate-array/
+
+4 Different Implementations
+"""
+
+from collections import deque
+
+
+# Time: O(n * k)     Space: O(1)
+def rotate_array_nk_time(nums: list[int], k: int) -> list[int]:
+    """
+    Takes the last k integers, and one by one, inserts them at the start of the array.
+
+    >>> rotate_array_nk_time([-1, 7, 25, 6], 3)
+    [7, 25, 6, -1]
+    >>> rotate_array_nk_time([4, 14, 2, -6, -9, 1, -37], 2)
+    [1, -37, 4, 14, 2, -6, -9]
+    >>> rotate_array_nk_time([19, -2, 5, 5, 11], 5)
+    [19, -2, 5, 5, 11]
+    >>> rotate_array_nk_time([1, 2, 4, 1, 2, 4], 3)
+    [1, 2, 4, 1, 2, 4]
+    >>> rotate_array_nk_time([8, -7, 22, -6], 9)
+    [-6, 8, -7, 22]
+    """
+
+    length = len(nums)
+    k = k % length
+    curr = length - k
+    for i in range(k):
+        dummy = nums[curr]
+        for j in range(curr - 1, i - 1, -1):
+            nums[j + 1] = nums[j]
+
+        nums[i] = dummy
+        curr += 1
+
+    return nums
+
+
+# Time: O(n)     Space: O(n)
+def rotate_array_n_space(nums: list[int], k: int) -> list[int]:
+    """
+    Creates new array consisting of last k integers in nums followed by remaining
+    integers in nums.
+
+    >>> rotate_array_n_space([-1, 7, 25, 6], 3)
+    [7, 25, 6, -1]
+    >>> rotate_array_n_space([4, 14, 2, -6, -9, 1, -37], 2)
+    [1, -37, 4, 14, 2, -6, -9]
+    >>> rotate_array_n_space([19, -2, 5, 5, 11], 5)
+    [19, -2, 5, 5, 11]
+    >>> rotate_array_n_space([1, 2, 4, 1, 2, 4], 3)
+    [1, 2, 4, 1, 2, 4]
+    >>> rotate_array_n_space([8, -7, 22, -6], 9)
+    [-6, 8, -7, 22]
+    """
+
+    return nums[-k:] + nums[:k]
+
+
+# Time: O(n)     Space: O(k)
+def rotate_array_k_space(nums: list[int], k: int) -> list[int]:
+    """
+    Uses a deque buffer of size k to shift each integer in nums by k places.
+
+    >>> rotate_array_k_space([-1, 7, 25, 6], 3)
+    [7, 25, 6, -1]
+    >>> rotate_array_k_space([4, 14, 2, -6, -9, 1, -37], 2)
+    [1, -37, 4, 14, 2, -6, -9]
+    >>> rotate_array_k_space([19, -2, 5, 5, 11], 5)
+    [19, -2, 5, 5, 11]
+    >>> rotate_array_k_space([1, 2, 4, 1, 2, 4], 3)
+    [1, 2, 4, 1, 2, 4]
+    >>> rotate_array_k_space([8, -7, 22, -6], 9)
+    [-6, 8, -7, 22]
+    """
+
+    length = len(nums)
+    k = k % length
+    buffer = deque(nums[length - k :])
+    for i in range(length):
+        buffer.append(nums[i])
+        nums[i] = buffer.popleft()
+
+    return nums
+
+
+# Time: O(n)     Space: O(1)
+def rotate_array_constant_space(nums: list[int], k: int) -> list[int]:
+    """
+    Reverse whole array. Then reverse first k elements. Then reverse remaining elements.
+
+    >>> rotate_array_constant_space([-1, 7, 25, 6], 3)
+    [7, 25, 6, -1]
+    >>> rotate_array_constant_space([4, 14, 2, -6, -9, 1, -37], 2)
+    [1, -37, 4, 14, 2, -6, -9]
+    >>> rotate_array_constant_space([19, -2, 5, 5, 11], 5)
+    [19, -2, 5, 5, 11]
+    >>> rotate_array_constant_space([1, 2, 4, 1, 2, 4], 3)
+    [1, 2, 4, 1, 2, 4]
+    >>> rotate_array_constant_space([8, -7, 22, -6], 9)
+    [-6, 8, -7, 22]
+    """
+
+    length = len(nums)
+    k = k % length
+
+    def reverse(left: int, right: int) -> None:
+        while left < right:
+            temp = nums[left]
+            nums[left] = nums[right]
+            nums[right] = temp
+            left += 1
+            right -= 1
+
+    reverse(0, length - 1)
+    reverse(0, k - 1)
+    reverse(k, length - 1)
+
+    return nums
+
+
+if __name__ == "__main__":
+    import doctest
+
+    doctest.testmod()