Arrays in C++

 

An array is a collection of elements of the same type, stored in contiguous memory locations. In C++, arrays allow you to store multiple values of the same type in a single variable, making it easier to work with large amounts of data.

Key Points:

• Arrays in C++ are zero-indexed, meaning the first element is accessed with index 0.
• Arrays can be of any data type (integers, floats, strings, etc.).
• The size of an array is fixed when it is declared and cannot be changed after initialization.

---

1️⃣ Declaring and Initializing Arrays in C++

Syntax:

dataType arrayName[arraySize];

Where:

• dataType is the type of elements in the array (e.g., int, float, char).
• arrayName is the name of the array.
• arraySize is the number of elements the array will hold.

Example: Declaring and Initializing an Integer Array

#include <iostream>
using namespace std;

int main() {
    // Declare an array of integers with 5 elements
    int numbers[5] = {1, 2, 3, 4, 5};

    // Accessing and printing array elements
    for (int i = 0; i < 5; i++) {
        cout << "Element " << i + 1 << ": " << numbers[i] << endl;
    }

    return 0;
}

Explanation:

• int numbers[5] declares an array of 5 integers.
• The array is initialized with the values {1, 2, 3, 4, 5}.
• We use a for loop to access and print each element.

Output:

Element 1: 1
Element 2: 2
Element 3: 3
Element 4: 4
Element 5: 5

---

2️⃣ Accessing Array Elements

Each element in an array can be accessed using its index. The first element is accessed using index 0, the second element with index 1, and so on.

Example: Accessing Array Elements by Index

#include <iostream>
using namespace std;

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

    // Accessing elements using indices
    cout << "First element: " << numbers[0] << endl;
    cout << "Second element: " << numbers[1] << endl;
    cout << "Third element: " << numbers[2] << endl;
    cout << "Fourth element: " << numbers[3] << endl;
    cout << "Fifth element: " << numbers[4] << endl;

    return 0;
}

Explanation:

• We use the index inside square brackets (numbers[index]) to access each element.
• The program outputs each element in the array by its respective index.

Output:

First element: 10
Second element: 20
Third element: 30
Fourth element: 40
Fifth element: 50

---

3️⃣ Multidimensional Arrays

C++ supports multidimensional arrays, which are arrays of arrays. The most common example is the 2D array.

Syntax for 2D Array:

dataType arrayName[rowSize][columnSize];

Example: 2D Array

#include <iostream>
using namespace std;

int main() {
    // Declare and initialize a 2D array (3x3 matrix)
    int matrix[3][3] = {
        {1, 2, 3},
        {4, 5, 6},
        {7, 8, 9}
    };

    // Accessing and printing elements of a 2D array
    for (int i = 0; i < 3; i++) {
        for (int j = 0; j < 3; j++) {
            cout << matrix[i][j] << " ";
        }
        cout << endl;
    }

    return 0;
}

Explanation:

• The 2D array matrix[3][3] is initialized with values in rows and columns.
• We use two nested for loops to access and print each element in the 2D array.

Output:

1 2 3
4 5 6
7 8 9

---

4️⃣ Array Size

The size of an array is fixed when it's declared. However, in C++, you can use the sizeof operator to determine the total size of the array in bytes.

Example: Finding Array Size

#include <iostream>
using namespace std;

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

    // Find the total size of the array in bytes
    int size = sizeof(numbers) / sizeof(numbers[0]);  // Total size divided by size of one element

    cout << "Number of elements in the array: " << size << endl;

    return 0;
}

Explanation:

• The expression sizeof(numbers) gives the total size of the array in bytes.
• sizeof(numbers[0]) gives the size of one element in the array.
• By dividing the total size by the size of one element, we get the number of elements in the array.

Output:

Number of elements in the array: 5

---

5️⃣ Array Input from User

You can also take input from the user to populate an array.

Example: User Input for Array

#include <iostream>
using namespace std;

int main() {
    int numbers[5];

    // Taking input for each element of the array
    cout << "Enter 5 numbers: " << endl;
    for (int i = 0; i < 5; i++) {
        cin >> numbers[i];  // Input each element
    }

    // Display the entered numbers
    cout << "You entered: ";
    for (int i = 0; i < 5; i++) {
        cout << numbers[i] << " ";
    }
    cout << endl;

    return 0;
}

Explanation:

• The user is prompted to input 5 numbers, which are stored in the numbers array.
• The program then prints out the entered numbers.

Output (Example when the user enters 1 2 3 4 5):

Enter 5 numbers: 
1
2
3
4
5
You entered: 1 2 3 4 5

---

6️⃣ Key Points to Remember:

• Array size is fixed at the time of declaration.
• Arrays are zero-indexed in C++, meaning the first element has an index of 0.
• You can use multidimensional arrays for matrices or tables.
• You can calculate the size of an array using the sizeof operator.
• Arrays can be initialized during declaration, and you can also take user input to populate them.

Would you like to explore dynamic arrays, array sorting, or array functions in C++?