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How to Rotate an Array to Left or Right in Java

What will happen if you have placed elements incorrectly in an array or placed them slightly left or right to the position where they should be? Let’s discuss array rotation in detail…

In this case, you can either delete the array and store it again or simply rotate its placement,

Yes, you can rotate the elements in an array through array rotation and solve this issue . 

Since Array is a linear data structure, the elements are placed in a specific sequence. You can easily change the location of elements in a linear data structure given the sequence. 

This can easily be done in the case of arrays and this is the biggest difference between arraylist and linked lists. 

If you do not know the ways through which you can change the location of an element or rotate the elements inside an array, this article will serve as your one-stop solution. 

In this segment, we will explain how array rotation works, the general algorithm followed during the process, and different approaches to rotate an array to left or right. 

Let’s begin with laying down the foundation of this concept by understanding what array rotation is in simple terms. 

What is array rotation?

The process of rotating the elements in a linear array to their left or right direction is called array rotation. 

This process is carried out multiple times unless the elements are placed at the right position in an array. 

Simply, the elements will be moved to their left or right by a single position. In case of left rotation, the first letter moves to the end of the array. The rotation of elements in this case is done in a clockwise direction. 

Whereas, in the right array rotation, the last element is moved to the first or beginning of the array. You can also understand this concept as the array elements are rotated in an anti-clockwise direction while rotating an array to the right hand side. 

To know how this process is carried out, Let’s move to the next segment of this article. 

Steps to rotate Array 

Do you know algorithms are technical representations of steps to carry out a process? 

Understanding the algorithm will clarify the process of array rotation for you. Following are the general steps in which array rotation is done to the left or right:

Step 1

First of all, the code is initialized 

Step 2

Then, you have to declare an array. You can put as many elements you want in this array and name it adequately. 

Step 3

After this, you need to set the number of rotations i.e. n as a desired value (let’s say 3) 

Step 4

In the next step, display the original form of array on the screen

Step 5

Print each element of the array till the end or till the length of the array. Display one element at a time. 

Step 6

Assign a new variable, let’s say the name of variable is “first”

Step 7

Afterwards, assign the value of the next element to the variable and repeat the process

Step 8

Re-assign the value of the array element through the variable. 

Using these steps in a specific loop you can get an accurate output from your code. 

But do you think that this general approach will work for all the sizes of arrays and in all situations? Well, not really. 

For that you need to know about the methods and approaches through which you can perform array rotation.

Methods to rotate an array

There are different approaches through which you can change the position of elements in your array to the left or right. 

Following are the ways in which you can rotate an array to left or right direction:

  • Using Juggling Algorithm

It is as interesting as it sounds! 

In this algorithm, the whole array is divided into smaller and less complex sets of elements. These sets can be moved inside the sets as per the need of the code. 

Let’s take an example of an array of first 6 even integers. 

The array will look like {0, 2,4,6,8,10}. Now, as per the algorithm, we have to divide them in smaller sets. Here, we will divide them in sets of 2 elements at a time. So, the sets become {0, 2}, {4,6}, {8, 10}.

Hence, if we wish to move these sets in the left direction for just one unit, the array will look like

{4, 6,8,10,0,2}

You can also make a set of alternate elements like {4, 8}, {6, 10}, and so on. 

  • Through temporary array

The second method to rotate an array is through a temporary array. In this method, simply take the input array and store the elements that need to be moved in a temporary array. 

Let’s say that you want to move the first two elements to the right. Hence, you will have to store the first two elements in a different (temporary array). Afterward, simply move the array to the right by inputting the elements in an accurate manner. 

Then, place the temporary array elements at the end of this array to complete the process. 

  • By reversing method

You can perform array rotation by simply reversing the array. 

The array can be divided into two sets i.e. k elements and n-k elements. Each array will be reversed one by one and as an output, you will get your rotated array towards the right. 

You can also rotate the same array to the left by reversing it adequately; however, make sure you learn how to reverse an array for this method. 

  • By rotating each element

The most common and simple method is to change the position of each element one by one. In this method, the code takes longer to execute, however, the mechanism is easy to understand. 

Advantages of an Array Rotation

Arrays Are Cache Friendly

Values are stored close to each other in an array. So, the CPU can easily access it from the cache memory only. Because of this, iteration in an array becomes faster and saves you from extra computational steps that you have to carry out to access elements from the main memory. It will parse the array. Moreover, an array of references can take advantage of this fact. 

Arrays Are Memory Friendly

In an array, memory is allocated dynamically. This helps to save the memory in your system and also, does not block memory statistically. This feature of arrays also helps when the pre-defined allocated memory to an array is insufficient. Moreover, when the allocation is static, the data is stored in a defined container and is completely dependent on the data type that you are using.

Arrays Have Flexible Length

Another advantage of an array is that it has flexible length. Besides that, zero-length arrays are another important method to use to implement arrays of variable length. By deciding on constant memory to the data structure, you may only end up wasting memory if it is not used. So, when you assign zero-length arrays no memory is assigned or used. In that case, such arrays are considered pointers.

Winding up

The array rotation is one of the simplest and most efficient ways of changing the positions of the elements in an array. You can easily rotate an array clockwise or anticlockwise through different methods. 

Array rotation is one of the factors that gives an upper hand to arrays while observing the  difference between arraylist and linkedlist

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