Rotate Array

#leetcode #dsa #theabbie

Given an array, rotate the array to the right by k steps, where k is non-negative.

Example 1:

Input: nums = [1,2,3,4,5,6,7], k = 3
Output: [5,6,7,1,2,3,4]
Explanation:
rotate 1 steps to the right: [7,1,2,3,4,5,6]
rotate 2 steps to the right: [6,7,1,2,3,4,5]
rotate 3 steps to the right: [5,6,7,1,2,3,4]

Example 2:

Input: nums = [-1,-100,3,99], k = 2
Output: [3,99,-1,-100]
Explanation:
rotate 1 steps to the right: [99,-1,-100,3]
rotate 2 steps to the right: [3,99,-1,-100]

Constraints:

1 <= nums.length <= 105
-231 <= nums[i] <= 231 - 1
0 <= k <= 105

Follow up:

Try to come up with as many solutions as you can. There are at least three different ways to solve this problem.
Could you do it in-place with O(1) extra space?

SOLUTION:

class Solution:
    def reverse(self, nums, a, b):
        n = b - a
        for i in range(n // 2):
            nums[a + i], nums[a + n - i - 1] = nums[a + n - i - 1], nums[a + i]
        return nums

    def rotate(self, nums: List[int], k: int) -> None:
        n = len(nums)
        k = n - k % n
        self.reverse(nums, 0, k)
        self.reverse(nums, k, n)
        self.reverse(nums, 0, n)
        return nums