leetcode189. Rotate Array

189. 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.

解法

先整体反转，然后前k个反转，然后之后的反转。

public class Solution {
    public void rotate(int[] nums, int k) {
        if (nums == null || nums.length == 0 || k <= 0) {
            return;
        }

        int len = nums.length;
        k = k % len;
        swap(nums, 0, len - 1);
        swap(nums, 0, k - 1);
        swap(nums, k, len - 1);
    }
    private void swap(int[] nums, int left, int right) {
        while (left < right) {
            int temp = nums[left];
            nums[left] = nums[right];
            nums[right] = temp;
            left++;
            right--;
        }
    }
}