189. Rotate Array

[Tcdian]

189. Rotate Array

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

Follow up

• 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?

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 <= 2 * 10⁴
• -2³¹ <= nums[i] <= 2³¹ - 1
• 0 <= k <= 10⁵

[Tcdian]

Solution

• TypeScript Solution

/**
 Do not return anything, modify nums in-place instead.
 */
function rotate(nums: number[], k: number): void {
    k = k % nums.length;
    reverse(0, nums.length - 1);
    reverse(0, k - 1);
    reverse(k, nums.length - 1);

    function reverse(start: number, end: number) {
        while (start < end) {
            [nums[start], nums[end]] = [nums[end], nums[start]];
            start++;
            end--;
        }
    }
};