How to Dynamically Allocate an Array in C++?

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In C++, dynamic memory allocation allows us to allocate memory during runtime. Dynamic allocation in an array is particularly useful when the size of an array is not known at compile time and needs to be specified during runtime. In this article, we will learn how to dynamically allocate an array in C++.

Dynamic Allocation of Arrays in C++

In C++, we use the new operator for dynamic memory allocation . To allocate an array dynamically,

Start by declaring a pointer that will store the base address of the allocated array.
Next, use the new operator to reserve memory space to accommodate an array of a particular data type.
When making this allocation specify the size of the array that indicates how many elements it can contain. This specified size determines the amount of memory to be allocated.

Syntax to Dynamically Allocate Arrays

Below is the general syntax for dynamically allocating an array in C++.

data_type* pointer_variableName = new data_type[array_size];

Here,

data_type is the type of data that we want to store in the array.
* pointer_variableName declares a pointer variable.
new is a keyword used for dynamic memory allocation.
array_size is the size of the array we want to allocate.

C++ Program to Dynamically Allocate an Array

The below program demonstrates the dynamic array allocation in C++.

C++

// C++ program to demonstrate how to dynamically allocate
// array
#include <iostream>
using namespace std;

int main()
{
    // Take array size as input from user
    cout << "Enter the size of the array: ";
    int size;
    cin >> size;

    // Dynamically allocate an array
    int* arr = new int[size];

    // Assign values to the array elements
    for (int i = 0; i < size; i++) {
        arr[i] = i + 1;
    }

    // Print the array elements
    cout << "Elements of the array are: ";
    for (int i = 0; i < size; i++) {
        cout << arr[i] << " ";
    }
    cout << endl;

    // Deallocate the memory
    delete[] arr;

    return 0;
}

Output

Enter the size of the array: 5
Elements of the array are: 1 2 3 4 5

Time Complexity: O(1)
Auxilliary Space: O(n), where n is the size of the dynamically allocated array.

Note: Always remember to deallocate the memory using the delete[] operator after use to prevent memory leaks.

Tags:

#C++ Array Programs #C++-new and delete #CPP Examples #cpp-array #C++ #C++ Programs #CPP

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