LeetCode Rotate Array

 1 public class Solution {
 2     public void rotate(int[] nums, int k) {
 3         int len = nums.length;
 4         k = k % len;
 5         
 6         /*
 7         //Method 1, takes O(n) space, running in O(n) time
 8         
 9         int[] res = new int[len];
10         
11         for(int i = 0;i<len;i++){
12             res[i] = nums[(i+len-k)%len];
13         }
14         
15         for(int i = 0;i<len;i++){
16             nums[i] = res[i];
17         }
18          */
19         
20         /*
21         //Method 2, takes O(k*n) time
22          
23          while(k>0){
24              int temp = nums[len - 1];
25             for(int i = len-1;i>0;i--)
26             {
27                 nums[i] = nums[i-1];
28             }
29             nums[0] = temp;
30             
31             k--;
32          }
33          */
34          
35          //Method 3, reverse the whole array, cut it into two parts, reverse each of them
36          reverse(nums, 0, len-1);
37          reverse(nums, 0, k-1);
38          reverse(nums, k, len-1);
39     }
40     
41     private void reverse(int[] arr, int left, int right){
42         while(left<right){
43             int temp = arr[left];
44             arr[left] = arr[right];
45             arr[right] = temp;
46             left++;
47             right--;
48         }
49     }
50 }