3 Ways To Contrary An Array Inward Coffee - Coding Interview Question

One of the mutual coding questions is, how produce yous opposite an array inwards Java? Well, at that topographic point are multiple ways to solve this problem. You tin opposite array past times writing your ain function, which loops through the array as well as swaps elements until the array is sorted. That's genuinely should yous live your get-go approach on interviews. Later yous tin impress the interviewer past times a twosome of other tricks, which is specific to Java evolution world. For example, yous tin opposite an array past times converting array to ArrayList as well as so utilization this code to opposite the ArrayList. You tin likewise utilization Apache Commons ArrayUtils.reverse() method to opposite whatever array inwards Java. This method is overloaded to opposite byte, short, long, int, float, double and String array. You tin utilization whatever of the method depending upon your array type.

Solution 1 - Revere array inwards Place

This is ane of the simplest ways to opposite an array inwards Java. This algorithm iterate over array as well as swap elements until yous achieve the midpoint. This is likewise known every bit reversing an array in-place because no additional buffer is used.

for(int i=0; i<array.length/2; i++){   int temp = array[i];   array[i] = array[array.length -i -1];   array[array.length -i -1] = temp; }

The fourth dimension complexity of this algorithm is O(n/2) which is O(N) because nosotros are iterating over array till midpoint only. This should live your solution on interviews, residuum of 2 methods are for practical utilization purpose.



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Solution 2 - Using ArrayList

Another uncomplicated agency to opposite an array inwards Java is past times get-go converting the array to List as well as so using Collections.reverse() method which takes a List as well as opposite the chemical component inwards linear time. You should utilization this approach if yous demand to opposite an array inwards your project. You tin opposite int, String or whatever type of array past times using this method. Let's encounter an event of reversing a String array inwards Java:

import java.util.ArrayList; import java.util.Arrays; import java.util.Collections; import java.util.List;   /**  * Simple Java Program to opposite an array  *  * @author Javin Paul  */ public class ArrayReverse {      public static void main(String args[])  {                String[] typesOfInsurance = {"Life Insurance", "Car Insurance", "Health Insurance"};       System.out.println("array earlier reverse: " + Arrays.toString(typesOfInsurance) );       List<String> listOfProducts = Arrays.asList(typesOfInsurance);             Collections.reverse(listOfProducts);       String[] reversed = listOfProducts.toArray(typesOfInsurance);       System.out.println("array subsequently reverse: " + Arrays.toString(reversed) );     }   }  Output array earlier reverse: [Life Insurance, Car Insurance, Health Insurance] array subsequently reverse: [Health Insurance, Car Insurance, Life Insurance] 

You tin encounter the fellowship of elements are opposite inwards the  final array returned past times toArray() method of List class.

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I know learning algorithms is non tardily as well as the books we have  e.g. Introduction of Algorithms and Algorithms fourth edition is likewise non really tardily for beginners, so I am promoting this mass to all beginner programmers. The practiced noesis of information construction as well as algorithms goes a long agency inwards your career as well as it doesn't affair whether yous produce coding inwards Java or C++, these concept stay same.

Solution 3 - By using ArrayUtils.reverse()

Apache common is an opened upwardly root library which provides several utility libraries which are essential for software evolution inwards Java. In fact, ane should past times default add together this library into their Java projects to complement JDK. Apache common lang provides an ArrayUtils shape which has overloaded reverse() methods to opposite int, float or object arrays inwards Java. This method likewise reverses the given array inwards house i.e. it doesn't render a novel array.

import java.util.Arrays; import org.apache.commons.lang3.ArrayUtils;   /**  * Java Program to opposite an array using Apache Commons Lang ArrayUtils  * class.  *  * @author Javin Paul  */ public class Pattern {      public static void main(String args[])  {                String[] assetClasses = {"bond", "equity", "gold", "real estate"};       System.out.println("Array earlier reversing: " + Arrays.toString(assetClasses));       ArrayUtils.reverse(assetClasses);       System.out.println("Array subsequently reversing: " + Arrays.toString(assetClasses));           }   }  Output Array earlier reversing: [bond, equity, gold, existent estate] Array subsequently reversing: [real estate, gold, equity, bond]

You tin encounter nosotros receive got manged to opposite the array inwards only ane work now. The ArrayUtils shape is from Apache common lang as well as yous demand to add together commons-lang3-3.4.jar into your application's classpath. Alternatively, if yous are using Maven so yous tin likewise add together next dependency inwards your pom.xml file.

 <dependency>         <groupId>org.apache.commons</groupId>         <artifactId>commons-lang3</artifactId>         <version>3.4</version>     </dependency>

That's all nigh how to opposite an array inwards Java. You receive got learned 3 dissimilar ways to solve this problem, first, yous tin the in-place algorithm to opposite array if yous were asked to solve this work on interviews. Second, yous tin utilization the ArrayList shape if yous demand to opposite the array inwards your projection as well as last, yous tin utilization utility method ArrayUtils.reverse() from Apache common lang library if your projection is already using it. If yous desire to a greater extent than of such questions from tech interviews, delight see Cracking the Coding Interview sixth Edition, it contains over 190 coding questions from dissimilar software companies, startups, investment banks, as well as service based companies.


Other array based coding problems for Java developers

• How to implement binary search inwards an array? (solution)
• How to discovery all pairs inwards array whose total is equal to k (solution)
• How to opposite an array inwards house inwards Java? (solution)
• How to banking concern fit if an array contains a item value? (solution)
• How to kind an array using bubble kind inwards Java? (solution)
• How to discovery duplicates from an unsorted array inwards Java? (solution)
• How to take duplicates from an array inwards Java? (solution)
• How to discovery the largest as well as smallest publish inwards an array without sorting? (solution)
• How to discovery ane missing publish inwards  a sorted array? (solution)
• How to take an chemical component from an array inwards Java? (solution)
• How to discovery transcend 2 numbers from given array? (solution)

Further Learning
The Coding Interview Bootcamp: Algorithms + Data Structures
Data Structures as well as Algorithms: Deep Dive Using Java
Algorithms as well as Data Structures - Part 1 as well as 2