leetcode 189: Rotate Array

解题思路：
对于字符串s，设s由字符串s1和s2两部分组成。先把s1逆序，再把s2逆序, 最后把s逆序，数组s就向右旋转了s2.size()个元素
问题描述：

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.

AC解，C++代码，菜鸟一个，请大家多多指正

class Solution {public:    void reverse(vector<int>& nums, int left, int right) {        while (left < right) {            int tmp = nums[left];            nums[left] = nums[right];            nums[right] = tmp;            left++;            right--;        }    }    void rotate(vector<int>& nums, int k) {        int nums_length = nums.size();        if (nums_length < 2) {            return ;        }        k = k % nums_length;        if (k < 1) {            return ;        }        reverse(nums, 0, nums_length - 1 - k);        reverse(nums, nums_length - k, nums_length - 1);        reverse(nums, 0, nums_length - 1);        return ;    }};