[LeetCode] 189. Rotate Array

 Problem : https://leetcode.com/problems/rotate-array/

A solution uses separate cache.

Time Complexity = O ( N )

Space Complexity = O ( N )

class Solution:
    def rotate(self, nums: List[int], k: int) -> None:
        """
        Do not return anything, modify nums in-place instead.
        """
        
        offset = len(nums) - (k % len(nums))
        
        tmp = nums[offset:] + nums[:offset]
        
        for i in range(len(nums)):
            nums[i] = tmp[i]

Reverse 3 times solution:

Time Compelxity = O ( N )

Space Complexity = O ( 1 )

class Solution:
    def rotate(self, nums: List[int], k: int) -> None:
        """
        Do not return anything, modify nums in-place instead.
        """
        
        def reverse(left, right):
            while left < right:
                nums[left], nums[right] = nums[right], nums[left]
                left += 1
                right -= 1
            
        
        N = len(nums)
        pivot = N - k % N
        
        # reverse the left side of pivot
        reverse(0, pivot-1)
        # reverse the right side of pivot
        reverse(pivot, N-1)
        # reverse the entire array
        reverse(0, N-1)