Search, insert and delete in an unsorted array

Difficulty Level : Basic
Last Updated : 28 Jun, 2021

In this post search, insert, and delete operations in an unsorted array are discussed.

Search Operation

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

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;
 
    return -1;
}
 
// Driver 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;
    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;
 
    return -1;
}
 
// Driver 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;
    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;
      
        return -1;
    }
      
    // Driver 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;
        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));
    }
}

Python

# Python program for searching in
# unsorted array
 
def findElement(arr, n, key):
    for i in range (n):
        if (arr[i] == key):
            return i
    return -1
  
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;
     
        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.

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;
 
    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.
?>

Javascript

<script>
 
// 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));
     
     
</script>

Output:

Element Found at Position: 5

Insert at the end

In an unsorted array, the insert operation is faster as compared to a sorted array because we don’t have to care about the position at which the element is to be placed.

C++

// C++ program to implement insert
// operation in an unsorted array.
#include <iostream>
using namespace std;
 
// Inserts a key in arr[] of given capacity.
// n is current size of arr[]. This
// function returns n + 1 if insertion
// is successful, else n.
int insertSorted(int arr[], int n,
                int key,
                int capacity)
{
 
    // Cannot insert more elements if n is
    // already more than or equal to capacity
    if (n >= capacity)
    return n;
 
    arr[n] = key;
 
    return (n + 1);
}
 
// Driver Code
int main()
{
    int arr[20] = {12, 16, 20, 40, 50, 70};
    int capacity = sizeof(arr) / sizeof(arr[0]);
    int n = 6;
    int i, key = 26;
 
    cout << "\n Before Insertion: ";
    for (i = 0; i < n; i++)
        cout << arr[i]<< " ";
 
    // Inserting key
    n = insertSorted(arr, n, key, capacity);
 
    cout << "\n After Insertion: ";
    for (i = 0; i < n; i++)
        cout << arr[i] << " ";
 
    return 0;
}
 
// This code is contributed by SHUBHAMSINGH10

C

// C program to implement insert
// operation in an unsorted array.
#include<stdio.h>
 
// Inserts a key in arr[] of given capacity.
// n is current size of arr[]. This
// function returns n + 1 if insertion
// is successful, else n.
int insertSorted(int arr[], int n,
                 int key,
                 int capacity)
{
 
    // Cannot insert more elements if n is
    // already more than or equal to capacity
    if (n >= capacity)
       return n;
 
    arr[n] = key;
 
    return (n + 1);
}
 
// Driver Code
int main()
{
    int arr[20] = {12, 16, 20, 40, 50, 70};
    int capacity = sizeof(arr) / sizeof(arr[0]);
    int n = 6;
    int i, key = 26;
 
    printf("\n Before Insertion: ");
    for (i = 0; i < n; i++)
        printf("%d  ", arr[i]);
 
    // Inserting key
    n = insertSorted(arr, n, key, capacity);
 
    printf("\n After Insertion: ");
    for (i = 0; i < n; i++)
        printf("%d  ",arr[i]);
 
    return 0;
}

Java

// Java program to implement insert
// operation in an unsorted array.
 
class Main
{
    // Function to insert a given key in
    // the array. This function returns n+1
    // if insertion is successful, else n.
    static int insertSorted(int arr[], int n,
                            int key,
                            int capacity)
    {
 
        // Cannot insert more elements if n
        // is already more than or equal to
        // capacity
        if (n >= capacity)
           return n;
      
        arr[n] = key;
      
        return (n + 1);
    }
      
    // Driver Code
    public static void main (String[] args)
    {  
        int[] arr = new int[20];
        arr[0] = 12;
        arr[1] = 16;
        arr[2] = 20;
        arr[3] = 40;
        arr[4] = 50;
        arr[5] = 70;
        int capacity = 20;
        int n = 6;
        int i, key = 26;
      
        System.out.print("Before Insertion: ");
        for (i = 0; i < n; i++)
            System.out.print(arr[i]+" ");
      
        // Inserting key
        n = insertSorted(arr, n, key, capacity);
      
        System.out.print("\n After Insertion: ");
        for (i = 0; i < n; i++)
            System.out.print(arr[i]+" ");
    }
}

Python

# Python program for inserting
# an element in an unsorted array
 
# method to insert element
def insert(arr, element):
    arr.append(element)
 
# declaring array and key to insert
arr = [12, 16, 20, 40, 50, 70]
key = 26
  
# array before inserting an element
print ("Before Inserting: ")
print (arr)
  
# array after Inserting element
insert(arr, key)
print("After Inserting: ")
print (arr)
 
# Thanks to Aditi Sharma for contributing
# this code   

C#

// C# program to implement insert
// operation in an unsorted array.
using System;
 
class main
{
     
    // Function to insert a given
    // key in the array. This
    // function  returns n + 1
    // if insertion is successful,
    // else n.
    static int insertSorted(int []arr, int n,
                            int key,
                            int capacity)
    {
         
        // Cannot insert more elements
        // if n is already more than
        // or equal to capacity
        if (n >= capacity)
        return n;
     
        arr[n] = key;
        return (n + 1);
    }
     
    // Driver Code
    public static void Main ()
    {
        int[] arr = new int[20];
        arr[0] = 12;
        arr[1] = 16;
        arr[2] = 20;
        arr[3] = 40;
        arr[4] = 50;
        arr[5] = 70;
        int capacity = 20;
        int n = 6;
        int i, key = 26;
     
        Console.Write("Before Insertion: ");
        for (i = 0; i < n; i++)
            Console.Write(arr[i]+" ");
            Console.WriteLine();
     
        // Inserting key
        n = insertSorted(arr, n, key, capacity);
     
        Console.Write("After Insertion: ");
        for (i = 0; i < n; i++)
            Console.Write(arr[i]+" ");
             
    }
}
 
// This code is contributed by vt_m.

PHP

<?php
// PHP program to implement insert
// operation in an unsorted array.
 
// Inserts a key in arr[] of given
// capacity. n is current size of arr[].
// This function returns n + 1 if
// insertion is successful, else n.
function insertSorted(&$arr, $n, $key,
                           $capacity)
{
 
    // Cannot insert more elements if n is
    // already more than or equal to capacity
    if ($n >= $capacity)
        return $n;
 
    array_push($arr, $key);
 
    return ($n + 1);
}
 
// Driver Code
 
$arr = array(12, 16, 20, 40, 50, 70);
$capacity = 20;
$n = 6;
$key = 26;
 
echo "Before Insertion: ";
for ($i = 0; $i < $n; $i++)
    echo $arr[$i] . " ";
 
// Inserting key
$n = insertSorted($arr, $n,
                  $key, $capacity);
 
echo "\nAfter Insertion: ";
for ($i = 0; $i < $n; $i++)
    echo $arr[$i] . " ";
     
// This code is contributed by
// Rajput-Ji
?>

Javascript

<script>
 
    // Javascript program to implement insert
    // operation in an unsorted array.
     
    // Function to insert a given
    // key in the array. This
    // function  returns n + 1
    // if insertion is successful,
    // else n.
    function insertSorted(arr, n, key, capacity)
    {
          
        // Cannot insert more elements
        // if n is already more than
        // or equal to capacity
        if (n >= capacity)
            return n;
      
        arr[n] = key;
        return (n + 1);
    }
     
    let arr = new Array(20);
    arr[0] = 12;
    arr[1] = 16;
    arr[2] = 20;
    arr[3] = 40;
    arr[4] = 50;
    arr[5] = 70;
    let capacity = 20;
    let n = 6;
    let i, key = 26;
 
    document.write("Before Insertion: ");
    for (i = 0; i < n; i++)
      document.write(arr[i]+" ");
    document.write("</br>");
 
    // Inserting key
    n = insertSorted(arr, n, key, capacity);
 
    document.write("After Insertion: ");
    for (i = 0; i < n; i++)
      document.write(arr[i]+" ");
     
</script>

Output:

Before Insertion: 12 16 20 40 50 70 
After Insertion: 12 16 20 40 50 70 26

Delete Operation

In the delete operation, the element to be deleted is searched using the linear search, and then delete operation is performed followed by shifting the elements.

C++

// C++ program to implement delete operation in a
// unsorted array
#include <iostream>
using namespace std;
 
// To search a key to be deleted
int findElement(int arr[], int n,
                int key);
 
// Function to delete an element
int deleteElement(int arr[], int n,
                int key)
{
    // Find position of element to be deleted
    int pos = findElement(arr, n, key);
 
    if (pos == - 1)
    {
        cout << "Element not found";
        return n;
    }
 
    // Deleting element
    int i;
    for (i = pos; i < n - 1; i++)
        arr[i] = arr[i + 1];
 
    return n - 1;
}
 
// 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;
 
    return - 1;
}
 
// Driver code
int main()
{
    int i;
    int arr[] = {10, 50, 30, 40, 20};
 
    int n = sizeof(arr) / sizeof(arr[0]);
    int key = 30;
 
    cout << "Array before deletion\n";
    for (i = 0; i < n; i++)
    cout << arr[i] <<" " ;
 
    n = deleteElement(arr, n, key);
 
    cout << "\n\nArray after deletion\n";
    for (i = 0; i < n; i++)
    cout << arr[i] << " ";
 
    return 0;
}
 
// This code is contributed by shubhamsingh10

C

// C program to implement delete operation in a
// unsorted array
#include<stdio.h>
 
// To search a key to be deleted
int findElement(int arr[], int n,
                int key);
 
// Function to delete an element
int deleteElement(int arr[], int n,
                  int key)
{
    // Find position of element to be deleted
    int pos = findElement(arr, n, key);
 
    if (pos == - 1)
    {
        printf("Element not found");
        return n;
    }
 
    // Deleting element
    int i;
    for (i = pos; i < n - 1; i++)
        arr[i] = arr[i + 1];
 
    return n - 1;
}
 
// 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;
 
    return - 1;
}
 
// Driver code
int main()
{
    int i;
    int arr[] = {10, 50, 30, 40, 20};
 
    int n = sizeof(arr) / sizeof(arr[0]);
    int key = 30;
 
    printf("Array before deletion\n");
    for (i = 0; i < n; i++)
      printf("%d  ", arr[i]);
 
    n = deleteElement(arr, n, key);
 
    printf("\nArray after deletion\n");
    for (i = 0; i < n; i++)
      printf("%d  ", arr[i]);
 
    return 0;
}

Java

// Java program to implement delete
// operation in an unsorted array
  
class Main
{
    // function to search a key to
    // be deleted
    static int findElement(int arr[], int n, int key)
    {
        int i;
        for (i = 0; i < n; i++)
            if (arr[i] == key)
                return i;
      
        return -1;
    }
     
    // Function to delete an element
    static int deleteElement(int arr[], int n, int key)
    {
        // Find position of element to be
        // deleted
        int pos = findElement(arr, n, key);
      
        if (pos == -1)
        {
            System.out.println("Element not found");
            return n;
        }
      
        // Deleting element
        int i;
        for (i = pos; i< n - 1; i++)
            arr[i] = arr[i + 1];
      
        return n - 1;
    }
      
    // Driver Code
    public static void main(String args[])
    {
        int i;
        int arr[] = {10, 50, 30, 40, 20};
      
        int n = arr.length;
        int key = 30;
      
        System.out.println("Array before deletion");
        for (i=0; i<n; i++)
          System.out.print(arr[i] + " ");
      
        n = deleteElement(arr, n, key);
      
        System.out.println("\n\nArray after deletion");
        for (i=0; i<n; i++)
          System.out.print(arr[i]+" ");
    }
}

Python

# Python program to delete an element
# from an unsorted array
 
# Declaring array and key to delete
arr = [10, 50, 30, 40, 20]
key = 30
  
print("Array before deletion:")
print arr
  
# deletes key if found in the array
# otherwise shows error not in list
arr.remove(key)
print("Array after deletion")
print(arr)
  
# This code is contributed by Aditi Sharma.

C#

// C# program to implement delete
// operation in an unsorted array
using System;
 
class main
{
    // Function to search a 
    // key to be deleted
    static int findElement(int []arr,
                           int n,
                           int key)
    {
         
        int i;
        for (i = 0; i < n; i++)
            if (arr[i] == key)
                return i;
     
        return -1;
    }
     
    // Function to delete an element
    static int deleteElement(int []arr,
                             int n,
                             int key)
    {
        // Find position of element
        // to be deleted
        int pos = findElement(arr, n, key);
     
        if (pos == - 1)
        {
            Console.WriteLine("Element not found");
            return n;
        }
     
        // Deleting element
        int i;
        for (i = pos; i < n - 1; i++)
            arr[i] = arr[i + 1];
     
        return n - 1;
    }
     
    // Driver Code
    public static void Main()
    {
        int i;
        int []arr = {10, 50, 30, 40, 20};
     
        int n = arr.Length;
        int key = 30;
     
        Console.Write("Array before deletion ");
        for (i = 0; i < n; i++)
        Console.Write(arr[i] + " ");
        Console.WriteLine();
     
        n = deleteElement(arr, n, key);
     
        Console.Write("Array after deletion ");
        for (i = 0; i < n; i++)
        Console.Write(arr[i]+" ");
    }
}
 
// This code is contributed by vt_m.

PHP

<?php
// PHP program to implement delete 
// operation in an unsorted array
 
// To search a key to be deleted
function findElement(&$arr, $n, $key)
{
    for ($i = 0; $i < $n; $i++)
        if ($arr[$i] == $key)
            return $i;
 
    return -1;
}
 
// Function to delete an element
function deleteElement(&$arr, $n, $key)
{
    // Find position of element to
    // be deleted
    $pos = findElement($arr, $n, $key);
 
    if ($pos == -1)
    {
        echo "Element not found";
        return $n;
    }
 
    // Deleting element
    for ($i = $pos; $i < $n - 1; $i++)
        $arr[$i] = $arr[$i + 1];
 
    return $n - 1;
}
 
// Driver code
$arr = array(10, 50, 30, 40, 20);
 
$n = count($arr);
$key = 30;
 
echo "Array before deletion\n";
for ($i = 0; $i < $n; $i++)
echo $arr[$i] . " ";
 
$n = deleteElement($arr, $n, $key);
 
echo "\nArray after deletion\n";
for ($i = 0; $i < $n; $i++)
echo $arr[$i] . " ";
 
// This code is contributed by
// Rajput-Ji
?>

Javascript

<script>
 
// Java script program to implement delete
// operation in an unsorted array
  
 
    // function to search a key to
    // be deleted
    function findElement(arr,n,key)
    {
        let i;
        for (i = 0; i < n; i++)
            if (arr[i] == key)
                return i;
      
        return -1;
    }
     
    // Function to delete an element
    function deleteElement(arr,n,key)
    {
        // Find position of element to be
        // deleted
        let pos = findElement(arr, n, key);
      
        if (pos == -1)
        {
            document.write("Element not found");
            return n;
        }
      
        // Deleting element
        let i;
        for (i = pos; i< n - 1; i++)
            arr[i] = arr[i + 1];
      
        return n - 1;
    }
      
    // Driver Code
     
        let i;
        let arr = [10, 50, 30, 40, 20];
      
        let n = arr.length;
        let key = 30;
      
        document.write("Array before deletion<br>");
        for (i=0; i<n; i++)
          document.write(arr[i] + " ");
      
        n = deleteElement(arr, n, key);
      
       document.write("<br><br>Array after deletion<br>");
        for (i=0; i<n; i++)
          document.write(arr[i]+" ");
     
// This code is contributed by sravan kumar Gottumukkala
</script>

Output:

Array before deletion
10 50 30 40 20 

Array after deletion
10 50 40 20

Time complexities:
Search: O(n)
Insert: O(1)
Delete: O(n)

Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.

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