189. Rotate Array(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.

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

思路：通过三次翻转来实现移位

class Solution {
public:
    void rotate(vector<int>& nums, int k) {
        int size = nums.size();
        k %= size;
        if(k == size || k == 0) return;

        reverse(nums,0,size-1-k);
        reverse(nums,size-k,size-1);
        reverse(nums, 0, size-1);
        return;
    }

    void reverse(vector<int>& nums, int start, int end){
        int tmp;
        while(start < end){
            tmp = nums[start];
            nums[start] = nums[end];
            nums[end] = tmp;
            start++;
            end--;
        }
    }
};