Deleting Elements in an Array | Array Operations

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

1. Deleting Elements from an Array when it is Unsorted
2. Deleting Elements from an Array when it is Sorted

Deleting Elements in an Array when it is Unsorted

In the delete operation, the element to be deleted is searched using the linear search, and then the 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's 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] << " ";

    // Function call
    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's 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]);

    // Function call
    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's 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] + " ");

        // Function call
        n = deleteElement(arr, n, key);

        System.out.println("\n\nArray after deletion");
        for (i = 0; i < n; i++)
            System.out.print(arr[i] + " ");
    }
}

Python3

# Python program to delete an element
# from an unsorted array

# Driver's code
if __name__ == '__main__':
    # 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();

        // Function call
        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.

Javascript

// 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

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] . " ";

// Function call
$n = deleteElement($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 Complexity: O(N) 
Auxiliary Space: O(1)

Deleting Elements in an Array when it is Sorted

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

Performing delete operation

Below is the implementation of the above approach:

C++

// C++ program to implement delete operation in a
// sorted array
#include <bits/stdc++.h>
using namespace std;

// To search a key to be deleted
int binarySearch(int arr[], int low, int high, int key);

/* Function to delete an element */
int deleteElement(int arr[], int n, int key)
{
    // Find position of element to be deleted
    int pos = binarySearch(arr, 0, n - 1, 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;
}

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
int main()
{
    int i;
    int arr[] = { 10, 20, 30, 40, 50 };

    int n = sizeof(arr) / sizeof(arr[0]);
    int key = 30;

    cout << "Array before deletion\n";
    for (i = 0; i < n; i++)
        cout << arr[i] << " ";

    // Function call
    n = deleteElement(arr, n, key);

    cout << "\n\nArray after deletion\n";
    for (i = 0; i < n; i++)
        cout << arr[i] << " ";
}

// This code is contributed by shubhamsingh10

C

// C program to implement delete operation in a
// sorted array
#include <stdio.h>

// To search a key to be deleted
int binarySearch(int arr[], int low, int high, int key);

/* Function to delete an element */
int deleteElement(int arr[], int n, int key)
{
    // Find position of element to be deleted
    int pos = binarySearch(arr, 0, n - 1, 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;
}

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
int main()
{
    int i;
    int arr[] = { 10, 20, 30, 40, 50 };

    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]);

    // Function call
    n = deleteElement(arr, n, key);

    printf("\n\nArray after deletion\n");
    for (i = 0; i < n; i++)
        printf("%d  ", arr[i]);
}

Java

// Java program to delete an
// element from a sorted array

class Main {

    // Binary search
    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);
    }

    /* Function to delete an element */
    static int deleteElement(int arr[], int n, int key)
    {
        // Find position of element to be deleted
        int pos = binarySearch(arr, 0, n - 1, 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, 20, 30, 40, 50 };

        int n = arr.length;
        int key = 30;

        System.out.print("Array before deletion:\n");
        for (i = 0; i < n; i++)
            System.out.print(arr[i] + " ");

        // Function call
        n = deleteElement(arr, n, key);

        System.out.print("\n\nArray after deletion:\n");
        for (i = 0; i < n; i++)
            System.out.print(arr[i] + " ");
    }
}

Python3

# Python program to implement delete operation in a
# sorted array

# /* Function to delete an element */


def deleteElement(arr, n, key):

    # Find position of element to be deleted
    pos = binarySearch(arr, 0, n - 1, key)

    if (pos == -1):
        print("Element not found")
        return n

    # Deleting element
    for i in range(pos, n - 1):
        arr[i] = arr[i + 1]

    return n - 1

# To search a key to be deleted


def binarySearch(arr, low, high, key):

    if (high < low):
        return -1
    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
if __name__ == "__main__":
    arr = [10, 20, 30, 40, 50]

    n = len(arr)
    key = 30

    print("Array before deletion")

    for i in range(n):
        print(arr[i], end=" ")

    # Function call
    n = deleteElement(arr, n, key)
    print("\n\nArray after deletion")
    for i in range(n):
        print(arr[i], end=" ")

# This code is contributed by shubhamsingh10

C#

// C# program to delete an
// element from a sorted array
using System;
public class GFG {

    // Binary search
    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);
    }

    /* Function to delete an element */
    static int deleteElement(int[] arr, int n, int key)
    {
        // Find position of element to be deleted
        int pos = binarySearch(arr, 0, n - 1, 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, 20, 30, 40, 50 };

        int n = arr.Length;
        int key = 30;

        Console.Write("Array before deletion:\n");
        for (i = 0; i < n; i++)
            Console.Write(arr[i] + " ");

        // Function call
        n = deleteElement(arr, n, key);

        Console.Write("\n\nArray after deletion:\n");
        for (i = 0; i < n; i++)
            Console.Write(arr[i] + " ");
    }
}

// This code is contributed by Rajput-Ji

Javascript

<script>

// JavaScript program to delete an
// element from a sorted array

    // binary search
    function binarySearch(arr,  low,  high,  key)
    {
        if (high < low)
            return -1;
        let 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);
    }

    /* Function to delete an element */
    function deleteElement( arr,  n,  key)
    {
        // Find position of element to be deleted
        let pos = binarySearch(arr, 0, n - 1, 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, 20, 30, 40, 50 ];

        let n = arr.length;
        let key = 30;

        document.write("Array before deletion:\n");
        for (i = 0; i < n; i++)
            document.write(arr[i] + " ");

        n = deleteElement(arr, n, key);

        document.write("<br>"+"Array after deletion:\n");
        for (i = 0; i < n; i++)
            document.write(arr[i] + " ");
 // this code is contributed by shivanisinghss2110

</script>

Output

Array before deletion
10 20 30 40 50 

Array after deletion
10 20 40 50 

Time Complexity: O(N). In the worst case all elements may have to be moved
Auxiliary Space: O(log N). An implicit stack will be used