How To Contrary Array Inwards House Inwards Java? Solution Amongst Explanation

Reversing an array sounds pretty easy, isn't it? It does sounds similar that, because all yous demand to do is create an array of same size, iterate through master copy array from cease to start too populate your novel array. Boom!!, yous own got got an array which has elements inward contrary lodge of master copy array, but work is yous own got used too additional array here, which makes infinite complexity of your solution O(n). You cannot travel this solution if array is large e.g. an array of x 1000000 orders too yous don't own got enough heap space available. Can nosotros arrive better? Can nosotros contrary array inward Java without using an additional buffer? Even If yous run across this enquiry inward your programming chore interview, yous volition survive for sure asked to reverse array inward place, without using an additional buffer as before solution takes lot of space. So directly your undertaking is to write a Java computer programme to contrary an array inward place. For the sake of this problem, yous tin assume that its an integer array (during interview, yous should inquire these enquiry to your interviewer, because holler for correct enquiry to fill upwards the gap inward requirement is a trait of adept programmer too highly appreciated on both telephonic too face-to-face interviews). Key indicate to sympathize hither is that yous demand to contrary the same array, yous cannot travel or thence other array but i or 2 variable is fine. You are every bit good non allowed to travel whatever opened upwards source library or Java API which tin contrary the array direct e.g. whatever method from java.util.Arrays cast except Arrays.toString()to print arrays inward Java. So directly the requirement is clear, what approach comes inward your mind? how do yous solve this problem?

Java Program to Reverse Array In Place

The get-go affair which comes inward my hear is to loop through array too swap the elements of array e.g. swap get-go chemical component amongst terminal element, swap instant chemical component amongst instant terminal chemical component until yous achieve the middle of the array. This way, all elements of array volition survive reversed without using whatever additional buffer. Key affair to give-up the ghost along inward hear inward this algorithm is that yous solely demand to iterate till middle element, if yous become beyond that too then yous cease upwards swapping elements twice too number inward same array. Some of yous volition survive puzzled, what is length of array is even? In that illustration at that spot volition survive 2 middle chemical component too nosotros demand to swap them, that's why your loop status should survive index <= middle too non index < middle. Here middle index is nix but length/2. Remember, nosotros are using partitioning operator, which agency if length is 8 too then it volition supply four too when length is seven it volition supply 3. So inward illustration of fifty-fifty length, the middle chemical component volition survive swapped twice, but inward illustration of strange length at that spot is only i middle chemical component too it volition non survive swapped.

It's been said fourth dimension too in i lawsuit again that a movie is worth a chiliad discussion too truthful to the point, this ikon explains the algorithm nosotros used to contrary array inward house quite well. You tin consider that how elements of arrays are swapped seat amongst each other too middle chemical component rest unchanged, amongst only 2 swapping nosotros own got reversed an array of v elements.

Here is our sample Java computer programme to contrary array inward place, solution is uncomplicated too slow to follow, but don't forget to await my JUnit tests to sympathize it fleck more.

import java.util.Arrays;  /**  * Java Program to demonstrate how to contrary an array inward place.  */ public class ArrayReversalDemo {      public static void main(String[] args) {         int[] numbers = {1, 2, 3, 4, 5, 6, 7};         reverse(numbers);     }      /**      * contrary the given array inward house       * @param input      */     public static void reverse(int[] input) {         System.out.println("original array : " + Arrays.toString(input));                  // treatment null, empty too i chemical component array         if(input == null || input.length <= 1){             return;         }                         for (int i = 0; i < input.length / 2; i++) {             int temp = input[i]; // swap numbers             input[i] = input[input.length - 1 - i];             input[input.length - 1 - i] = temp;         }          System.out.println("reversed array : " + Arrays.toString(input));     }           }  Output master copy array : [1, 2, 3, 4, 5, 6, 7] reversed array : [7, 6, 5, 4, 3, 2, 1] master copy array : [] master copy array : null master copy array : [1, 2, 3, 4, 5, 6] reversed array : [6, 5, 4, 3, 2, 1] master copy array : [1]

You tin consider inward output hither that input array is reversed properly too inward illustration of null, empty too array amongst only i element, same array is returned.

JUnit tests

Here is my suite of JUnit tests for our reverse(int[] input)  method. I own got made certain to examine our solution tin handgrip null, empty array, an array amongst only i element, too array amongst fifty-fifty or strange number of elements. You tin fifty-fifty examine drive this problem. Writing Unit examine is a adept practice too during Interview yous must write JUnit examine fifty-fifty if Interview has non asked for it. This shows that yous are a professional person software developer too yous assist for your trade.

import static org.junit.Assert.assertArrayEquals;  import org.junit.Test;  public class ArrayReversalDemoTest {          @Test     public void testReverseWithEvenLengthOfArray(){         int[] numbers = {1, 2, 3, 4, 5, 6};         HelloWorld.reverse(numbers);         assertArrayEquals(new int[]{6, 5, 4, 3, 2, 1}, numbers);     }          @Test     public void testReverseWithOddLengthOfArray(){         int[] numbers = {1, 2, 3, 4, 5, 6, 7};         HelloWorld.reverse(numbers);         assertArrayEquals(new int[]{7, 6, 5, 4, 3, 2, 1}, numbers);     }          @Test     public void testReverseWithEmptyArray(){         int[] numbers = {};         HelloWorld.reverse(numbers);         assertArrayEquals(new int[]{}, numbers);     }          @Test     public void testReverseWithNullArray(){         int[] numbers = null;         HelloWorld.reverse(numbers);         assertArrayEquals(null, numbers);     }          @Test     public void testReverseWithJustOneElementArray(){         int[] numbers = {1};         HelloWorld.reverse(numbers);         assertArrayEquals(new int[]{1}, numbers);     }     }

too hither is the output of running our unit of measurement tests, they all pass.

That's all virtually how to contrary array inward house inward Java. Time complexity of this method is O(n/2) or O(n) because it solely iterate through one-half of the array, but its inward O(n) because response fourth dimension increases inward same lodge every bit input increases. As a task, tin yous discovery a faster solution of this problem?


Further Learning
Data Structures too Algorithms: Deep Dive Using Java
solution)

How to discovery prime number factors of an integer inward Java? (solution)

How to cheque if LinkedList contains whatever bicycle inward Java? (solution)

Write a Program take away duplicates from array without using Collection API? (program)

How to contrary String inward Java without using API methods? (Solution)

Write a method to cheque if 2 String are Anagram of each other? (method)

Write a component subdivision to discovery middle chemical component of linked listing inward i pass? (solution)

How to solve Producer Consumer Problem inward Java. (solution)

Write a computer programme to discovery get-go non repeated characters from String inward Java? (program)

How to cheque if a number is binary inward Java? (answer)

Write a Program to Check if a number is Power of Two or not? (program)

Write a computer programme to cheque if a number is Prime or not? (solution)

Write a method to count occurrences of  a grapheme inward String? (Solution)

How to discovery Fibonacci sequence upto a given Number? (solution)

How to cheque if a number is Armstrong number or not? (solution)

Write a method to take away duplicates from ArrayList inward Java? (Solution)

Write a computer programme to cheque if a number is Palindrome or not? (program)

Write a computer programme to cheque if Array contains duplicate number or not? (Solution)

How to calculate Sum of Digits of a number inward Java? (Solution)

How to foreclose Deadlock inward Java? (solution)

How to discovery largest prime number cistron of a number inward Java? (solution)

How to calculate factorial using recursion inward Java? (algorithm)

How to declare too initialize 2 dimensional array inward Java? (solution)

Write a computer programme to discovery missing number inward a sorted array? (algorithm)

How to search chemical component inward array inward Java? (solution)

10 Points virtually Array inward Java? (must know facts)

How to discovery top 2 maximum on integer array inward Java? (solution)

How to kind array using bubble kind algorithm? (algorithm)

Thanks for reading this article thence far. If yous similar this article too then delight portion amongst your friends too colleagues. If yous own got whatever enquiry or dubiousness too then delight allow us know too I'll endeavor to discovery an reply for you.

Share this post