Rotate Array

Description

Given an integer array nums, 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?

Code

$O(n)$ space

class Solution {
public:
    void rotate(vector<int>& nums, int k) {
        vector<int> temp(nums);
        int n = nums.size();
        for(int i = 0; i < nums.size(); i++){
            temp[(i + k) % n] = nums[i];
        }
        swap(nums, temp);
    }
};
 
 

$O(1)$ space using reverse

class Solution {
public:
    void rotate(vector<int>& nums, int k) {
		
        reverse(nums.begin(), nums.end() - k);
        reverse(nums.end() - k, nums.end());
        reverse(nums.begin(), nums.end());
    }
};

Source

• Rotate Array - LeetCode