189. Rotate Array

Medium

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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?

class Solution:
    def rotate(self, nums: List[int], k: int) -> None:
        k = k%len(nums)
        
        # Revese Whole Array
        left = 0
        right = len(nums)-1
        while left < right:
            nums[left], nums[right] = nums[right], nums[left]
            left += 1
            right -= 1
        # Reverse first k elements
        left = 0
        right = k-1
        while left < right:
            nums[left], nums[right] = nums[right], nums[left]
            left += 1
            right -= 1
        # Reverse elements from k to end
        left = k
        right = len(nums)-1
        while left < right:
            nums[left], nums[right] = nums[right], nums[left]
            left += 1
            right -= 1