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Rotate Array

Updated: Mar 25, 2021

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

Follow up:

  • 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?


Example 1:

Input: nums = [1,2,3,4,5,6,7], 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: nums = [-1,-100,3,99], 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]

Constraints:

  • 1 <= nums.length <= 2 * 104

  • -231 <= nums[i] <= 231 - 1

  • 0 <= k <= 105

Solution:


class Solution {
    public void rotate(int[] nums, int k) {
        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[] n,int start, int end)
    {
        while(start<end)
        {
         int temp=n[start];
        n[start]=n[end];
        n[end]=temp;
        start++;
        end--;  
        }
        
    }
}

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