leetcode_189_Rotate Array(easy)(C++)

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.

[show hint]

Related problem: Reverse Words in a String II

第一种：

class Solution {

public:

    void rotate(vector& nums, int k) {

        

        

       const int n = nums.size();

       k = k % n;

       vector backup(nums.end() - k, nums.end());

       for(int i = n - 1 ; i >= k ; --i)

       {

           nums[i] = nums[i-k];

       }

       for( int i = 0; i < k; i++)

       {

           nums[i] = backup[i];

       }

    }

};

第二种:

class Solution {
public:
    void rotate(vector& nums, int k) {
        
        
       const int n = nums.size();
       k = k % n;
       reverse(nums.begin(), nums.end());
       reverse(nums.begin() + k, nums.end());
       reverse(nums.begin(), nums.begin() + k ) ;
    }
};

vector中的begin指的是容器的第一个元素，end指的容器中最后一个元素的下一个元素