Recursive linear search java: In the previous article, we have discussed about Java Program to Check Perfect Number by Using Recursion
In this program we are going to see how to implement linear search by using recursion by Java programming language.
Java Program to Implement Linear Search by Using Recursion
Lets start with an example.
Assume there is an array say A which has 5 elements {77, 82, 100, 17, 95}
We need to check if the specified element is present or not.
Example 99: Not present, 100: present
Now let’s see different ways to implement linear search by using Recursion.
Method-1: Java Program to Implement Linear Search By Using Static Input and Recursion
Approach:
- Declare an integer Array ‘
arr’ and initialize it elements. - Declare and initiate an integer variable say ‘
value’ as 94 - Call a user defined method
search()and pass the array ‘arr[]’ with first index ‘0’, last index ‘arr.length-1’ and the specific element to be searched ‘value’ as parameter. - Inside the user defined method, check if the last index is less than the first index then return -1 else if the first index is equal to value then return first index else call search() method recursively to search until that specific value is found inside the array.
- Now, the result of user defined method
search()is stored in an integer variable say ‘index’. - Print the result.
Program:
import java.util.*;
import java.io.*;
public class Main
{
// defined main() method where the program starts executing
public static void main(String[] args)
{
//declare and initialize an integer variable array arr[]
int[] arr = {77, 82, 100, 17, 95};
//declare and initialize an integer variable ‘value’ to search that specific number inside the array
int value = 94;
//calling the user defined method search()
//and store the result value inside an integer variable say ‘index’
int index = search(arr, 0, arr.length-1, value);
// check if the value is present in the array then print the result
if (index != -1)
System.out.println("The element " + value + " is present at index " + index);
else
System.out.println("The element " + value + " is not present in the array");
}
// defined search() method with arr[], first index, last index and value as parameter to search that specific value inside the array
public static int search(int arr[], int firstIndex, int lastIndex, int value)
{
// if the last index is less than the first index then return -1
if (lastIndex < firstIndex)
return -1;
// if the first index is equal to value then return first index
if (arr[firstIndex] == value)
return firstIndex;
// else call search() method recursively to search until that specific value is found inside the array
return search(arr, firstIndex+1, lastIndex, value);
}
}
Output: The element 94 is not present in the array
Method-2: Java Program to Implement Linear Search By Using User Input and Recursion
Approach:
- Create a scanner class.
- Declare an integer variable say ‘
n’ - Prompt the user to enter the size of the array as value of
n. - Declare an integer Array ‘
arr[]’ . - Prompt the user to enter the elements inside the array.
- Declare and initiate an integer variable say ‘
value’ - Prompt the user to enter the value of
value - Call a user defined method
search()and pass the array ‘arr[]’ with first index ‘0’, last index ‘arr.length-1’ and the specific element to be searched ‘value’ as parameter. - Inside the user defined method, check if the last index is less than the first index then return -1 else if the first index is equal to value then return first index else call search() method recursively to search until that specific value is found inside the array.
- Now, the result of user defined method
search()is stored in an integer variable say ‘index’. - Print the result.
Program:
import java.util.*;
import java.io.*;
public class Main
{
public static void main(String[] args)
{
// create a scanner class
Scanner s = new Scanner(System.in);
System.out.println("Enter no. of elements you want in array:");
//prompting the user to enter a integer value
int n = s.nextInt();
// declare the array and initialize it with user input
int arr[] = new int[n];
//get all the elements sequentially inside the array
System.out.println("Enter all the elements in the array:");
for(int i = 0; i < n; i++)
arr[i] = s.nextInt();
// declare the specific value to be search inside the array
System.out.println("Enter the specific element you want to search in the array:");
int value = s.nextInt();
//calling the user defined method search()
//and store the result value inside an integer variable say ‘index’
int index = search(arr, 0, arr.length-1, value);
// check if the value is present in the array then print the result
if (index != -1)
System.out.println("The element " + value + " is present at index " + index);
else
System.out.println("The element " + value + " is not present in the array");
}
// defined search() method with arr[], first index, last index and value as parameter to search that specific value inside the array
public static int search(int arr[], int firstIndex, int lastIndex, int value)
{
// if the last index is less than the first index then return -1
if (lastIndex < firstIndex)
return -1;
// if the first index is equal to value then return first index
if (arr[firstIndex] == value)
return firstIndex;
// else call search() method recursively to search until that specific value is found inside the array
return search(arr, firstIndex+1, lastIndex, value);
}
}
Output: Enter no. of elements you want in array: 7 Enter all the elements in the array: 1 17 78 86 94 22 175 Enter the specific element you want to search in the array: 94 The element 94 is present at index 4
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