In the last article about searching and sorting, you have learned the binary search algorithm and today I'll teach you another fundamental searching algorithm called

The time complexity of linear search algorithm is O(n) where n is the number of elements in the target array, which shows its slower than binary search algorithm, whose time complexity was O(logN) because it was dividing the array into two part in every iteration.

Actually the learning order is to first learn linear search and then the binary search but and we all learned that way but I found that when you first code binary search, then linear search becomes extremely easy and it also easier to reason about its time and space complexity and performance, hence I presented this algorithm after binary search.

Btw, if you enjoy learning algorithms and want to see the application of algorithms in the real world but struggle with calculating time and space complexity, I would suggest going through

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Here is our program to implement a linear search in Java. It performs liner search in a given array. It first asks users to enter the size of the array and then each element. Once the array is filled, it asks the user for the target element. It then performs linear search and returns the index of the target element in the array, if it exists.

If you want, you can also modify the algorithm to work on a pre-populated array, instead of asking the user to provide. The logic of linear search algorithm is encapsulated in the linearSearch(int[] input, int target) method, you can use as you wish. You need to just pass the integer array and target number and it will return you the index of the target element in the array.

If you like to learn more about searching and sorting algorithm, I suggest you check out then

In practice, the algorithm work is just like given in this diagram:

And, if you like books then you must check out the

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Anyway, here is our Java program to implement a linear search algorithm:

You can see that our program has successfully able to find the index of the target element using Linear search or Sequential Search Algorithm in Java. If you are more curious you can also run this program with a large array, something which you can create programmatically.

For example int[] numbers = new int[Integer.MAX_VALUE] will create a really large array and if you just put 1 in the last index and then search for it, your program will take a long time to respond because it has to go through 2^32-1 elements to reach the last element.

That's all about

Data Structures and Algorithms: Deep Dive Using Java

Algorithms and Data Structures - Part 1 and 2

Data Structures in Java: An Interview Refresher

Cracking the Coding Interview - 189 Questions and Solutions

Other

**Linear search**. Linear search is nothing but iterating over the array and comparing each element with target element to see if they are equal since we search the array sequential from start to end, this is also known as**sequential search**or**linear search**. It is very slow as compared to binary search because you have to compare each element with every other element and definitely not suitable for a large array. It's practically useful only in case of the small array up to 10 to 15 numbers. In the worst case, you need to check all elements to confirm if the target element exists in an array or not.The time complexity of linear search algorithm is O(n) where n is the number of elements in the target array, which shows its slower than binary search algorithm, whose time complexity was O(logN) because it was dividing the array into two part in every iteration.

Actually the learning order is to first learn linear search and then the binary search but and we all learned that way but I found that when you first code binary search, then linear search becomes extremely easy and it also easier to reason about its time and space complexity and performance, hence I presented this algorithm after binary search.

Btw, if you enjoy learning algorithms and want to see the application of algorithms in the real world but struggle with calculating time and space complexity, I would suggest going through

**Data Structures and Algorithms: Deep Dive Using Java**, one of the comprehensive course on Data Structure and Algorithm on Udemy. This will not only teach you essential algorithms but fundamentals data structure like the array, linked list, hash table, binary tree, etc.##
__Java Program to implement Linear Search__

Here is our program to implement a linear search in Java. It performs liner search in a given array. It first asks users to enter the size of the array and then each element. Once the array is filled, it asks the user for the target element. It then performs linear search and returns the index of the target element in the array, if it exists.If you want, you can also modify the algorithm to work on a pre-populated array, instead of asking the user to provide. The logic of linear search algorithm is encapsulated in the linearSearch(int[] input, int target) method, you can use as you wish. You need to just pass the integer array and target number and it will return you the index of the target element in the array.

If you like to learn more about searching and sorting algorithm, I suggest you check out then

**Algorithms and Data Structures - Part 1 and 2**, two great courses from Pluralsight. They are not completely free but you need to sign up for trial, which gives you 10 days free access to all courses in Pluralsight.In practice, the algorithm work is just like given in this diagram:

And, if you like books then you must check out the

**Grokking Algorithms by Aditya Bhargava,**one of the most interesting book on algorithms with lots of easy to understand diagrams, visuals, and real-world explanation. I am reading this book now and it's truly interesting.##
__Linear Search Algorithm in Java__

Anyway, here is our Java program to implement a linear search algorithm:import java.util.Scanner; /* * Java Program to implement binary search algorithm * using recursion */ public class LinearSearchAlgorithm { public static void main(String[] args) { Scanner commandReader = new Scanner(System.in); System.out .println("Welcome to Java Program to perform linear search on int array"); System.out.println("Enter length of array : "); int length = commandReader.nextInt(); int[] input = new int[length]; System.out.printf("Enter %d numbers %n", length); for (int i = 0; i < length; i++) { input[i] = commandReader.nextInt(); } System.out.println("Please enter target number"); int target = commandReader.nextInt(); int index = linearSearch(input, target); if (index == -1) { System.out.printf("Sorry, %d is not found in array %n", target); } else { System.out.printf("%d is found in array at index %d %n", target, index); } commandReader.close(); } /** * Java method to liner search an element in array * * @param input * @param target * @return index of target element or -1 if not found */ public static int linearSearch(int[] input, int target) { for (int i = 0; i < input.length; i++) { if (input[i] == target) { return i; } } return -1; } } Output Welcome to Java Program to perform linear search on int array Enter length of array : 7 Enter 7 numbers 1 2 2 3 4 5 6 Please enter target number 4 4 is found in array at index 4 Welcome to Java Program to perform linear search on int array Enter length of array : 3 Enter 3 numbers 22 33 44 Please enter target number 2222 is found in the array at index 0

You can see that our program has successfully able to find the index of the target element using Linear search or Sequential Search Algorithm in Java. If you are more curious you can also run this program with a large array, something which you can create programmatically.

For example int[] numbers = new int[Integer.MAX_VALUE] will create a really large array and if you just put 1 in the last index and then search for it, your program will take a long time to respond because it has to go through 2^32-1 elements to reach the last element.

That's all about

**how to implement linear search in Java**. You can see that our algorithm is working correctly and it found out the right index for target value, 4 in the first case and 22 in the second case. It's one of the simplest searching algorithms but very important to learn and understand linked list data structure, which only supports linear search algorithm.**Further Learning**Data Structures and Algorithms: Deep Dive Using Java

Algorithms and Data Structures - Part 1 and 2

Data Structures in Java: An Interview Refresher

Cracking the Coding Interview - 189 Questions and Solutions

Other

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**P. S.**- If you are looking for some Free Algorithms courses to improve your understanding of Data Structure and Algorithms, then you should also check the**Easy to Advanced Data Structures**course on Udemy. It's authored by a Google Software Engineer and Algorithm expert and its completely free of cost.
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