LeetCode 189. Rotate Array

Description

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

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

Example 1:

Input: [1,2,3,4,5,6,7] and 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: [-1,-100,3,99] and 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]

Note:

  • Try to come up as many solutions as you can, there are at least 3 different ways to solve this problem.
  • Could you do it in-place with O(1) extra space?

Explanation

Use a temp array to store the element in rotating order

Python Solution

class Solution:
    def rotate(self, nums: List[int], k: int) -> None:
        """
        Do not return anything, modify nums in-place instead.
        """
        temps = []
        
        for i in range(len(nums) - k, len(nums)):
            temps.append(nums[i])
        
        for i in range(0, len(nums) - k):
            temps.append(nums[i])
            
        for i in range(0, len(nums)):            
            nums[i] = temps[i]     
  • Time complexity: O(N).
  • Space complexity: O(N).

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