189. Rotate Array

Rotate Array

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

[show hint] Hint: Could you do it in-place with O(1) extra space?

Related problem: Reverse Words in a String II

Credits:Special thanks to @Freezen for adding this problem and creating all test cases.

Solution

public class Solution {
      public void rotate(int[] nums, int k) {
        if (nums == null || nums.length <= 1) return;
        int size = nums.length;

        k %= size;
        swap(nums, 0, size - k - 1);
        swap(nums, size - k, size - 1);
        swap(nums, 0, size - 1);
    }

    private void swap(int[] nums, int start, int end) {
        while (start < end) {
            int temp = nums[start];
            nums[start] = nums[end];
            nums[end] = temp;
            start ++;
            end --;
        }
    }
}