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.

Stunning Trick:

http://zhuixin8.com/2016/10/09/%E7%99%BD%E8%AF%9DLeetCode-189-Rotate-Array/

Rotate right:

• reverse the entire array
• reverse the [0, k-1]
• reverse the [k,n]

Rotate left:

• reverse the [0, k-1]
• reverse the [k, n]
• reverse the entire array

public class Solution {
    public void reverse(int[] nums, int start, int end)
    {
        int temp;
        if(start >= end)
        {
            return;
        }
        temp = nums[start];
        nums[start] = nums[end];
        nums[end] = temp;
        reverse(nums, start+1, end-1);
    }

    public void rotate(int[] nums, int k) {

        k %= nums.length;
        reverse(nums, 0, nums.length-1);
        reverse(nums, 0, k-1);
        reverse(nums, k, nums.length-1);
    }
}

Other Solution

https://leetcode.com/articles/rotate-array/#approach-4-using-reverse-accepted