leetcode 189. Rotate Array

Seawolf

Given an array, rotate the array to the right by k steps, where k is non-negative.

Example 1:

Input: [1,2,3,4,5,6,7] and k = 3
Output: [5,6,7,1,2,3,4]
Explanation:
rotate 1 steps to the right: [7,1,2,3,4,5,6]
rotate 2 steps to the right: [6,7,1,2,3,4,5]
rotate 3 steps to the right: [5,6,7,1,2,3,4]
Example 2:

Input: [-1,-100,3,99] and k = 2
Output: [3,99,-1,-100]
Explanation: 
rotate 1 steps to the right: [99,-1,-100,3]
rotate 2 steps to the right: [3,99,-1,-100]
Note:

Try to come up as many solutions as you can, there are at least 3 different ways to solve this problem.
Could you do it in-place with O(1) extra space?

class Solution {
    public void rotate(int[] nums, int k) {
        if(nums.length ==0 || nums.length ==1) return;
    
        if(k == 0) return;
        
        if(k > nums.length) k = k % nums.length;
        int[] res = new int[nums.length];
        
        for(int i = 0; i < nums.length; i++){
            
            if(i <  k){
                
                res[i] = nums[i+nums.length-k];
                
            }else if(i >=  k){
                
                res[i] = nums[i-k]; 
            }
        }
        
        for(int i = 0; i < nums.length; i++){
            
            nums[i] = res[i];
        }
        
    }
}

class Solution {
    public void rotate(int[] nums, int k) {
        
        if(nums.length == 0 || nums.length == 1) return;
        
        if(k>nums.length) k = k % nums.length;

        reverse(nums,0, nums.length-1);
        reverse(nums,0,k-1);
        reverse(nums,k,nums.length-1);
        
    }
    
    public void reverse(int[] nums, int start, int end){
        
        while(end - start >= 1 && start < end){
            
            int i = nums[start];
            
            nums[start] = nums[end];
            
            nums[end] =i;
            
            start++;
            end--;
        }
    }
}