[LeetCode] Rotate Array

Problem

Rotate an array of n elements to the right by k steps.

Example

For example, with n = 7 and k = 3, the array [1,2,3,4,5,6,7] is rotated to [5,6,7,1,2,3,4].

Note

Try to come up as many solutions as you can, there are at least 3 different ways to solve this problem.

Hint

Could you do it in-place with O(1) extra space?
Related problem: Reverse Words in a String II

Solution

class Solution {
    public void rotate(int[] nums, int k) {
        //1234567, k=3
        //4321567
        //4321765
        //5671234
        
        int len = nums.length;
        k = k % len;
        reverse(nums, 0, len-1-k);
        reverse(nums, len-k, len-1);
        reverse(nums, 0, len-1);
        return;
    }
    public void reverse(int[] nums, int start, int end) {
        while (start < end) {
            int temp = nums[start];
            nums[start] = nums[end];
            nums[end] = temp;
            start++;
            end--;
        }
    }
}