Search, insert and delete in an unsorted array

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

Recommended: Please solve it on “PRACTICE” first, before moving on to the solution.

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. 
?> 

Output:

Element Found at Position: 5

Insert at the end

In an unsorted array, the insert operation is faster as compared to 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<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 capcity 
    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  
        // capcity 
        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 capcity  
        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 capcity  
    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 
?> 

Output:

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

Delete Operation

In 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<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 
?> 

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)

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