Rotate Array

Description

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.

思路

三步反转法

(X^TY^T)^T = YX

这里需要特别注意，向右移动的步数 k 有可能大于数组的长度，因此要做个取模处理。

实现代码

class Solution {
    public void rotate(int[] nums, int k) {
        int n = nums.length;
        k %= n;
        reverse(nums, 0, n - k - 1);
        reverse(nums, n - k, n - 1);
        reverse(nums, 0, n - 1);
    }
    
    private void reverse(int[] nums, int from, int to) {
        while (from < to) {
            int temp = nums[from];
            nums[from++] = nums[to];
            nums[to--] = temp;
        }
    }
}