【LeetCode】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.[show hint]

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

Related problem: Reverse Words in a String II

Solution 1：reverse[1,2,3,4]=[4,3,2,1], reverse[5,6,7]=[7,6,5], reverse[4,3,2,1,7,6,5]=[5,6,7,1,2,3,4]

 #include<algorithm>
 class Solution {
 public:
     void rotate(vector<int>& nums, int k) {      //runtime:24ms
         int n=nums.size();
         k %= n;
         reverse(nums.begin(),nums.begin()+n-k);
         reverse(nums.begin()+n-k,nums.end());
         reverse(nums.begin(),nums.end());
     }
 };

Solution 2：超时

 class Solution {
 public:
     void rotate(vector<int>& nums, int k) {
         int n=nums.size();
         k %= n;
         while(k--){
             int temp=nums[n-];
             for(int i=n-;i>;i--){
                 nums[i]=nums[i-];
             }
             nums[]=temp;
         }
     }
 };

Solution 3:

 void rotate(int nums[], int n, int k) {
     k = k % n;
     if (k == ) return;
     int *temp = new int[n];
     memcpy(temp, nums+(n-k), sizeof(int)*k);
     memcpy(temp+k, nums, sizeof(int)*(n-k));
     memcpy(nums, temp, sizeof(int)*n);
     delete[] temp;
 }