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.

把最右边的数移到最左边，移动k次

C++（19ms）：

class Solution {
public:
    void Reverse(vector<int>& nums,int left , int right){
        while(left < right){
            swap(nums[left++],nums[right--]) ;
        }
    }
    void rotate(vector<int>& nums, int k) {
        int len = nums.size() ;
        k %= len ;
        k = len - k ;
        Reverse(nums,0,k-1) ;
        Reverse(nums,k,len-1) ;
        Reverse(nums,0,len-1) ;
    }
};