Data Modelling & AI Data Structure & Algorithm

Searching Elements in an Array | Array Operations

By Thapelo Manthata

23 June 2025

0

In this post, we will look into search operation in an Array, i.e., how to search an element in an Array, such as:

Searching in an Unsorted Array using Linear Search
Searching in a Sorted Array using Linear Search
Searching in a Sorted Array using Binary Search

Searching operations in an Unsorted Array using Linear Search

In an unsorted array, the search operation can be performed by linear traversal from the first element to the last element, i.e. Linear Search

Coding implementation of the search operation:

C++

// C++ program to implement linear
// search in unsorted array
#include <bits/stdc++.h>
using namespace std;
 
// Function to implement search operation
int findElement(int arr[], int n, int key)
{
    int i;
    for (i = 0; i < n; i++)
        if (arr[i] == key)
            return i;
 
    // If the key is not found
    return -1;
}
 
// Driver's Code
int main()
{
    int arr[] = { 12, 34, 10, 6, 40 };
    int n = sizeof(arr) / sizeof(arr[0]);
 
    // Using a last element as search element
    int key = 40;
 
    // Function call
    int position = findElement(arr, n, key);
 
    if (position == -1)
        cout << "Element not found";
    else
        cout << "Element Found at Position: "
             << position + 1;
 
    return 0;
}
 
// This code is contributed
// by Akanksha Rai

C

// C program to implement linear
// search in unsorted array
#include <stdio.h>
 
// Function to implement search operation
int findElement(int arr[], int n, int key)
{
    int i;
    for (i = 0; i < n; i++)
        if (arr[i] == key)
            return i;
 
    // If the key is not found
    return -1;
}
 
// Driver's Code
int main()
{
    int arr[] = { 12, 34, 10, 6, 40 };
    int n = sizeof(arr) / sizeof(arr[0]);
 
    // Using a last element as search element
    int key = 40;
 
    // Function call
    int position = findElement(arr, n, key);
 
    if (position == -1)
        printf("Element not found");
    else
        printf("Element Found at Position: %d",
               position + 1);
 
    return 0;
}

Java

// Java program to implement linear
// search in unsorted arrays
 
class Main {
 
    // Function to implement
    // search operation
    static int findElement(int arr[], int n, int key)
    {
        for (int i = 0; i < n; i++)
            if (arr[i] == key)
                return i;
 
        // If the key is not found
        return -1;
    }
 
    // Driver's Code
    public static void main(String args[])
    {
        int arr[] = { 12, 34, 10, 6, 40 };
        int n = arr.length;
 
        // Using a last element as search element
        int key = 40;
 
        // Function call
        int position = findElement(arr, n, key);
 
        if (position == -1)
            System.out.println("Element not found");
        else
            System.out.println("Element Found at Position: "
                               + (position + 1));
    }
}

Python3

# Python program for searching in
# unsorted array
 
 
def findElement(arr, n, key):
    for i in range(n):
        if (arr[i] == key):
            return i
 
    # If the key is not found
    return -1
 
 
# Driver's code
if __name__ == '__main__':
    arr = [12, 34, 10, 6, 40]
    key = 40
    n = len(arr)
 
    # search operation
    index = findElement(arr, n, key)
    if index != -1:
        print("Element Found at position: " + str(index + 1))
    else:
        print("Element not found")
 
    # Thanks to Aditi Sharma for contributing
    # this code

C#

// C# program to implement linear
// search in unsorted arrays
using System;
 
class main {
    // Function to implement
    // search operation
    static int findElement(int[] arr, int n, int key)
    {
        for (int i = 0; i < n; i++)
            if (arr[i] == key)
                return i;
 
        // If the key is not found
        return -1;
    }
 
    // Driver Code
    public static void Main()
    {
        int[] arr = { 12, 34, 10, 6, 40 };
        int n = arr.Length;
 
        // Using a last element as
        // search element
        int key = 40;
        int position = findElement(arr, n, key);
 
        if (position == -1)
            Console.WriteLine("Element not found");
        else
            Console.WriteLine("Element Found at Position: "
                              + (position + 1));
    }
}
 
//  This code is contributed by vt_m.

Javascript

// Javascript program to implement linear 
// search in unsorted array
 
 
// Function to implement search operation 
function findElement( arr, n, key)
{
    let i;
    for (i = 0; i < n; i++)
        if (arr[i] == key)
            return i;
 
    return -1;
}
 
 
     
    // Driver program
     
    let arr = [12, 34, 10, 6, 40];
    let n = arr.length;
 
    // Using a last element as search element
    let key = 40;
    let position = findElement(arr, n, key);
 
    if (position == - 1)
        document.write("Element not found");
    else
        document.write("Element Found at Position: "
             + (position + 1));

PHP

<?php
// PHP program to implement linear 
// search in unsorted array
 
// Function to implement
// search operation 
function findElement($arr, $n, $key)
{
    $i;
    for ($i = 0; $i < $n; $i++)
        if ($arr[$i] == $key)
            return $i;
     
      // If the key is not found
    return -1;
}
 
// Driver Code
$arr = array(12, 34, 10, 6, 40);
$n = sizeof($arr);
 
// Using a last element
// as search element
$key = 40;
$position = findElement($arr, $n, $key);
 
if ($position == - 1)
    echo("Element not found");
else
    echo("Element Found at Position: " . ($position + 1));
 
// This code is contributed by Ajit.
?>

Output

Element Found at Position: 5

Time Complexity: O(N)
Auxiliary Space: O(1)

Searching in a Sorted Array using Linear Search

In a sorted array, the most trivial method for search operation is by using Linear Search.

Below is the implementation of the above approach:

C++

// C++ program to implement linear
// search in sorted array
#include <bits/stdc++.h>
using namespace std;
 
// Function to implement search operation
int findElement(int arr[], int n, int key)
{
    int i;
    for (i = 0; i < n; i++)
        if (arr[i] == key)
            return i;
 
    // If the key is not found
    return -1;
}
 
// Driver's Code
int main()
{
    int arr[] = { 5, 6, 7, 8, 9, 10 };
    int n = sizeof(arr) / sizeof(arr[0]);
 
    // Using a last element as search element
    int key = 10;
 
    // Function call
    int position = findElement(arr, n, key);
 
    if (position == -1)
        cout << "Element not found";
    else
        cout << "Element Found at Position: "
             << position + 1;
 
    return 0;
}
 
// This code is contributed
// by Akanksha Rai

C

// C program to implement linear
// search in sorted array
#include <stdio.h>
 
// Function to implement search operation
int findElement(int arr[], int n, int key)
{
    int i;
    for (i = 0; i < n; i++)
        if (arr[i] == key)
            return i;
 
    // If the key is not found
    return -1;
}
 
// Driver's Code
int main()
{
    int arr[] = { 5, 6, 7, 8, 9, 10 };
    int n = sizeof(arr) / sizeof(arr[0]);
 
    // Using a last element as search element
    int key = 10;
 
    // Function call
    int position = findElement(arr, n, key);
 
    if (position == -1)
        printf("Element not found");
    else
        printf("Element Found at Position: %d",
               position + 1);
 
    return 0;
}

Java

// Java program to implement linear
// search in sorted arrays
 
class Main {
 
    // Function to implement
    // search operation
    static int findElement(int arr[], int n, int key)
    {
        for (int i = 0; i < n; i++)
            if (arr[i] == key)
                return i;
 
        // If the key is not found
        return -1;
    }
 
    // Driver's Code
    public static void main(String args[])
    {
        int arr[] = { 5, 6, 7, 8, 9, 10 };
        int n = arr.length;
 
        // Using a last element as search element
        int key = 10;
 
        // Function call
        int position = findElement(arr, n, key);
 
        if (position == -1)
            System.out.println("Element not found");
        else
            System.out.println("Element Found at Position: "
                               + (position + 1));
    }
}

Python3

# Python program for searching in
# sorted array
 
 
def findElement(arr, n, key):
    for i in range(n):
        if (arr[i] == key):
            return i
 
    # If the key is not found
    return -1
 
 
# Driver's code
if __name__ == '__main__':
    arr = [5, 6, 7, 8, 9, 10]
    key = 10
    n = len(arr)
 
    # search operation
    index = findElement(arr, n, key)
    if index != -1:
        print("Element Found at position: " + str(index + 1))
    else:
        print("Element not found")
 
    # Thanks to Aditi Sharma for contributing
    # this code

C#

// C# program to implement linear
// search in sorted arrays
using System;
 
class main {
    // Function to implement
    // search operation
    static int findElement(int[] arr, int n, int key)
    {
        for (int i = 0; i < n; i++)
            if (arr[i] == key)
                return i;
 
        // If the key is not found
        return -1;
    }
 
    // Driver Code
    public static void Main()
    {
        int[] arr = { 5, 6, 7, 8, 9, 10 };
        int n = arr.Length;
 
        // Using a last element as
        // search element
        int key = 10;
        int position = findElement(arr, n, key);
 
        if (position == -1)
            Console.WriteLine("Element not found");
        else
            Console.WriteLine("Element Found at Position: "
                              + (position + 1));
    }
}
 
//  This code is contributed by vt_m.

Javascript

// Javascript program to implement linear 
// search in sorted array
 
 
// Function to implement search operation 
function findElement( arr, n, key)
{
    let i;
    for (i = 0; i < n; i++)
        if (arr[i] == key)
            return i;
 
    return -1;
}
 
 
     
    // Driver program
     
    let arr = [5, 6, 7, 8, 9, 10];
    let n = arr.length;
 
    // Using a last element as search element
    let key = 10;
    let position = findElement(arr, n, key);
 
    if (position == - 1)
        document.write("Element not found");
    else
        document.write("Element Found at Position: "
             + (position + 1));

PHP

<?php
// PHP program to implement linear 
// search in sorted array
 
// Function to implement
// search operation 
function findElement($arr, $n, $key)
{
    $i;
    for ($i = 0; $i < $n; $i++)
        if ($arr[$i] == $key)
            return $i;
     
      // If the key is not found
    return -1;
}
 
// Driver Code
$arr = array(5, 6, 7, 8, 9, 10);
$n = sizeof($arr);
 
// Using a last element
// as search element
$key = 10;
$position = findElement($arr, $n, $key);
 
if ($position == - 1)
    echo("Element not found");
else
    echo("Element Found at Position: " . ($position + 1));
 
// This code is contributed by Ajit.
?>

Output

Element Found at Position: 6

Time Complexity: O(N)
Auxiliary Space: O(1)

Searching in a Sorted Array using Binary Search

In a sorted array, the search operation can be performed efficiently by using binary search.

Below is the implementation of the above approach:

C++

// C++ program to implement binary search in sorted array
#include <bits/stdc++.h>
using namespace std;
 
int binarySearch(int arr[], int low, int high, int key)
{
    if (high < low)
        return -1;
    int mid = (low + high) / 2; /*low + (high - low)/2;*/
    if (key == arr[mid])
        return mid;
    if (key > arr[mid])
        return binarySearch(arr, (mid + 1), high, key);
    return binarySearch(arr, low, (mid - 1), key);
}
 
/* Driver code */
int main()
{
    // Let us search 3 in below array
    int arr[] = { 5, 6, 7, 8, 9, 10 };
    int n, key;
 
    n = sizeof(arr) / sizeof(arr[0]);
    key = 10;
 
    // Function call
    cout << "Index: " << binarySearch(arr, 0, n - 1, key)
         << endl;
    return 0;
}
 
// This code is contributed by NamrataSrivastava1

C

// C program to implement binary search in sorted array
#include <stdio.h>
 
int binarySearch(int arr[], int low, int high, int key)
{
    if (high < low)
        return -1;
    int mid = (low + high) / 2; /*low + (high - low)/2;*/
    if (key == arr[mid])
        return mid;
    if (key > arr[mid])
        return binarySearch(arr, (mid + 1), high, key);
    return binarySearch(arr, low, (mid - 1), key);
}
 
/* Driver Code */
int main()
{
    // Let us search 3 in below array
    int arr[] = { 5, 6, 7, 8, 9, 10 };
    int n, key;
 
    n = sizeof(arr) / sizeof(arr[0]);
    key = 10;
 
    // Function call
    printf("Index: %d\n", binarySearch(arr, 0, n - 1, key));
    return 0;
}

Java

// Java program to implement binary
// search in a sorted array
 
class Main {
    // function to implement
    // binary search
    static int binarySearch(int arr[], int low, int high,
                            int key)
    {
        if (high < low)
            return -1;
 
        /*low + (high - low)/2;*/
        int mid = (low + high) / 2;
        if (key == arr[mid])
            return mid;
        if (key > arr[mid])
            return binarySearch(arr, (mid + 1), high, key);
        return binarySearch(arr, low, (mid - 1), key);
    }
 
    /* Driver Code*/
    public static void main(String[] args)
    {
        int arr[] = { 5, 6, 7, 8, 9, 10 };
        int n, key;
        n = arr.length - 1;
        key = 10;
 
        // Function call
        System.out.println("Index: "
                           + binarySearch(arr, 0, n, key));
    }
}

Python3

# python 3  program to implement
# binary search in sorted array
 
 
def binarySearch(arr, low, high, key):
 
    mid = (low + high)/2
 
    if (key == arr[int(mid)]):
        return mid
 
    if (key > arr[int(mid)]):
        return binarySearch(arr,
                            (mid + 1), high, key)
 
    if (key < arr[int(mid)]):
        return binarySearch(arr, low, (mid-1), key)
 
    return 0
 
 
# Driver code
if __name__ == "__main__":
    # Let us search 3 in below array
    arr = [5, 6, 7, 8, 9, 10]
    n = len(arr)
    key = 10
 
    # Function call
    print("Index:", int(binarySearch(arr, 0, n-1, key)))
 
# This code is contributed by
# Smitha Dinesh Semwal

C#

// C# program to implement binary
// search in a sorted array
 
using System;
 
public class GFG {
 
    // function to implement
    // binary search
    public static int binarySearch(int[] arr, int low,
                                   int high, int key)
    {
        if (high < low) {
            return -1;
        }
 
        int mid = (low + high) / 2;
        if (key == arr[mid]) {
            return mid;
        }
        if (key > arr[mid]) {
            return binarySearch(arr, (mid + 1), high, key);
        }
        return binarySearch(arr, low, (mid - 1), key);
    }
 
    /* Driver Code */
    public static void Main(string[] args)
    {
        int[] arr = new int[] { 5, 6, 7, 8, 9, 10 };
        int n, key;
        n = arr.Length;
        key = 10;
 
        // Function call
        Console.WriteLine(
            "Index: " + binarySearch(arr, 0, n - 1, key));
    }
}
 
// This code is contributed by Shrikant13

Javascript

<script>
 
 
// Javascript program to implement 
// binary search in sorted array
 
function binarySearch( arr, low, high, key)
{
    if (high < low)
        return -1;
        /*low + (high - low)/2;*/
    let mid = Math.trunc((low + high) / 2); 
    if (key == arr[mid])
        return mid;
    if (key > arr[mid])
        return binarySearch(arr, (mid + 1), high, key);
    return binarySearch(arr, low, (mid - 1), key);
}
 
     
    // Driver program
     
    // Let us search 3 in below array
    let arr = [ 5, 6, 7, 8, 9, 10 ];
    let n, key;
 
    n = arr.length;
    key = 10;
 
    document.write( "Index: " + binarySearch(arr, 0, n - 1, key)
    + "</br>");
     
     
</script>

PHP

<?php
// PHP program to implement
// binary search in sorted array
 
function binarySearch($arr, $low, 
                      $high, $key) 
{
    if ($high < $low) 
    return -1;
     
    $mid = (int)($low + $high) / 2;
     
    if ($key == $arr[(int)$mid])
        return $mid;
     
    if ($key > $arr[(int)$mid]) 
        return binarySearch($arr, ($mid + 1), 
                            $high, $key);
     
    return (binarySearch($arr, $low, 
                        ($mid -1), $key));
}
 
// Driver Code
 
// Let us search 3 in below array
$arr = array(5, 6, 7, 8, 9, 10);
$n = count($arr);
$key = 10;
 
// Function call
echo "Index: ", (int)binarySearch($arr, 0, 
                                  $n-1, $key);
 
// This code is contributed by
// Srathore
?>

Output

Index: 5

Time Complexity: O(log(n)) Using Binary Search
Auxiliary Space: O(log(n)) due to recursive calls, otherwise iterative version uses Auxiliary Space of O(1).

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Searching Elements in an Array | Array Operations

Searching operations in an Unsorted Array using Linear Search

C++

C

Java

Python3

C#

Javascript

PHP

Searching in a Sorted Array using Linear Search

C++

C

Java

Python3

C#

Javascript

PHP

Searching in a Sorted Array using Binary Search

C++

C

Java

Python3

C#

Javascript

PHP

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