Insert Element at the Beginning of an Array (original) (raw)
Last Updated : 07 Nov, 2024
Given an array of integers, the task is to insert an element at the beginning of the array.
**Examples:
**Input: arr[] = [10, 20, 30, 40], ele = 50
**Output: [50, 10, 20, 30, 40]**Input: arr[] = [], ele = 20
**Output: [20]
Table of Content
[Approach 1] Using Built-In Methods
We will use library methods like **insert() in C++, Python and C#, **add() in Java and **unshift() in JavaScript.
C++ `
// C++ program to insert given element at the beginning // of an array
#include #include using namespace std;
int main() {
vector arr = {10, 20, 30, 40};
int element = 50;
cout << "Array before insertion\n";
for (int i = 0; i < arr.size(); i++)
cout << arr[i] << " ";
// Insert element at the beginning
arr.insert(arr.begin(), element);
cout << "\nArray after insertion\n";
for (int i = 0; i < arr.size(); i++)
cout << arr[i] << " ";
return 0;}
Java
// Java program to insert a given element at the beginning of an arraY
import java.util.ArrayList; import java.util.Arrays;
class GfG { public static void main(String[] args) { ArrayList arr = new ArrayList<>(Arrays.asList(10, 20, 30, 40)); int element = 50; System.out.println("Array before insertion"); for (int i = 0; i < arr.size(); i++) System.out.print(arr.get(i) + " ");
// Insert element at the beginning
arr.add(0, element);
System.out.println("\nArray after insertion");
for (int i = 0; i < arr.size(); i++)
System.out.print(arr.get(i) + " ");
}}
Python
Python program to insert a given element at the beginning
of an array
arr = [10, 20, 30, 40] element = 50 print("Array before insertion") for i in range(len(arr)): print(arr[i], end=" ")
Insert element at the beginning
arr.insert(0, element)
print("\nArray after insertion") for i in range(len(arr)): print(arr[i], end=" ")
C#
// C# program to insert a given element at the beginning // of an array
using System; using System.Collections.Generic;
class GfG { static void Main() { List arr = new List { 10, 20, 30, 40 }; int element = 50; Console.WriteLine("Array before insertion"); foreach (int num in arr) Console.Write(num + " ");
// Insert element at the beginning
arr.Insert(0, element);
Console.WriteLine("\nArray after insertion");
foreach (int num in arr)
Console.Write(num + " ");
}}
JavaScript
// JavaScript program to insert a given element at the beginning // of an array
let arr = [10, 20, 30, 40]; let element = 50; console.log("Array before insertion"); console.log(arr.join(" "));
// Insert element at the beginning arr.unshift(element);
console.log("Array after insertion"); console.log(arr.join(" "));
`
Output
Array before insertion 10 20 30 40 Array after insertion 50 10 20 30 40
**Time Complexity: O(n), where n is the size of the array.
[Approach 2] Using Custom Method
To insert an element at the beginning of an array, first shift all the elements of the array to the right by 1 index and after shifting insert the new element at 0th position.
C++ `
// C++ program to insert given element at the beginning // of an array
#include #include using namespace std;
int main() {
vector arr = {10, 20, 30, 40, 0};
int n = 4;
int element = 50;
cout << "Array before insertion\n";
for (int i = 0; i < n; i++)
cout << arr[i] << " ";
// Shift all elements to the right
for(int i = n - 1; i >= 0; i--) {
arr[i + 1] = arr[i];
}
// Insert new element at the beginning
arr[0] = element;
cout << "\nArray after insertion\n";
for (int i = 0; i <= n; i++)
cout << arr[i] << " ";
return 0;}
C
// C program to insert given element at the beginning // of an array
#include <stdio.h>
int main() { int arr[6] = {10, 20, 30, 40, 0}; int n = 4; int element = 50;
printf("Array before insertion:\n");
for (int i = 0; i < n; i++) {
printf("%d ", arr[i]);
}
// Shift elements to the right
for (int i = n - 1; i >= 0; i--) {
arr[i + 1] = arr[i];
}
// Insert the new element at the beginning
arr[0] = element;
printf("\nArray after insertion:\n");
for (int i = 0; i <= n; i++) {
printf("%d ", arr[i]);
}
return 0;}
Java
// Java program to insert given element at the beginning // of an array
import java.util.Arrays;
class GfG { public static void main(String[] args) { int[] arr = {10, 20, 30, 40, 0}; int n = 4; int element = 50;
System.out.println("Array before insertion");
for (int i = 0; i < n; i++) {
System.out.print(arr[i] + " ");
}
// Shift all elements to the right
for (int i = n - 1; i >= 0; i--) {
arr[i + 1] = arr[i];
}
// Insert new element at the beginning
arr[0] = element;
System.out.println("\nArray after insertion");
for (int i = 0; i <= n; i++) {
System.out.print(arr[i] + " ");
}
}}
Python
Python program to insert given element at the beginning
of an array
arr = [10, 20, 30, 40, 0] n = 4 element = 50
print("Array before insertion") for i in range(n): print(arr[i], end=" ")
Shift all elements to the right
for i in range(n - 1, -1, -1): arr[i + 1] = arr[i]
Insert new element at the beginning
arr[0] = element
print("\nArray after insertion") for i in range(n + 1): print(arr[i], end=" ")
C#
// C# program to insert given element at the beginning // of an array
using System;
class GfG { static void Main() { int[] arr = {10, 20, 30, 40, 0}; int n = 4; int element = 50;
Console.WriteLine("Array before insertion");
for (int i = 0; i < n; i++) {
Console.Write(arr[i] + " ");
}
// Shift all elements to the right
for (int i = n - 1; i >= 0; i--) {
arr[i + 1] = arr[i];
}
// Insert new element at the beginning
arr[0] = element;
Console.WriteLine("\nArray after insertion");
for (int i = 0; i <= n; i++) {
Console.Write(arr[i] + " ");
}
}}
JavaScript
// JavaScript program to insert given element at the beginning // of an array
let arr = [10, 20, 30, 40, 0]; let n = 4; let element = 50;
console.log("Array before insertion"); console.log(arr.slice(0, n).join(" "));
// Shift all elements to the right for (let i = n - 1; i >= 0; i--) { arr[i + 1] = arr[i]; }
// Insert new element at the beginning arr[0] = element;
console.log("Array after insertion"); console.log(arr.join(" "));
`
Output
Array before insertion 10 20 30 40 Array after insertion 50 10 20 30 40
**Time Complexity: O(n), where n is the size of the array.