What are arrays and how to use them in C++

In C++ an Array is a collection of elements of the same type, of fixed size stored in contiguous memory locations.

Each element of the array can be accessed using a numerical index, starting from zero. For this, the [] operator is used.

Array declaration

The basic syntax for declaring an array in C++ is:

Type arrayName[size];

For example, to declare an array of integers with 5 elements:

int myNumbers[5];

Creating and initializing arrays

Once an array is declared, it can be initialized in several ways:

int numbers[5] = {1, 2, 3, 4, 5};

int numbers[5] = {1, 2}; // The array is initialized as {1, 2, 0, 0, 0}

int numbers[] = {1, 2, 3, 4, 5}; // The size of the array is automatically adjusted to 5

Using the array

Accessing elements

Each element of an array is accessed using an index, which starts at 0. The syntax to access an element is:

arrayName[index]

For example:

int numbers[] = {1, 2, 3, 4, 5};
int firstNumber = numbers[0]; // firstNumber will be 1

Modifying elements

You can modify the elements of the array by assigning new values to specific indices:

int numbers[] = {1, 2, 3, 4, 5};
numbers[2] = 10; // The third element of the array will now be 10

Common operations with arrays

Array length

To get the number of elements in an array, you can use the sizeof operator:

int numbers[] = {1, 2, 3, 4, 5};
int length = sizeof(numbers) / sizeof(numbers[0]); // length will be 5

Sorting an array

To sort arrays you can use the sort function from the standard library <algorithm>:

#include <algorithm>

int numbers[] = {5, 3, 1, 4, 2};
std::sort(numbers, numbers + 5); // Sorts the array in ascending order

Reversing an array

To reverse the order of the elements, you can also use the reverse function from <algorithm>:

#include <algorithm>

int numbers[] = {1, 2, 3, 4, 5};
std::reverse(numbers, numbers + 5); // Reverses the array

Multidimensional arrays

Arrays can have more than one dimension, allowing for the storage of data in more complex structures like matrices.

Example of a two-dimensional array

int matrix[2][3] = {
    {1, 2, 3},
    {4, 5, 6}
};

In this example, matrix is a two-dimensional array with 2 rows and 3 columns.

Accessing elements in multidimensional arrays

std::cout << "Element in row 1, column 2: " << matrix[1][2] << std::endl; // Prints 6

Practical examples

#include <iostream>

int main() {
    int numbers[] = {1, 2, 3, 4, 5};
    int sum = 0;

    for (int i = 0; i < 5; i++) {
        sum += numbers[i];
    }

    double average = static_cast<double>(sum) / 5;
    std::cout << "The average is: " << average << std::endl;

    return 0;
}

#include <iostream>

int main() {
    int numbers[] = {1, 2, 3, 4, 5};
    int maximum = numbers[0];

    for (int i = 1; i < 5; i++) {
        if (numbers[i] > maximum) {
            maximum = numbers[i];
        }
    }

    std::cout << "The maximum value is: " << maximum << std::endl;

    return 0;
}

#include <iostream>

int main() {
    int numbers[] = {1, 2, 3, 4, 5};
    int value = 3;
    int count = 0;

    for (int i = 0; i < 5; i++) {
        if (numbers[i] > value) {
            count++;
        }
    }

    std::cout << "There are " << count << " elements greater than " << value << std::endl;

    return 0;
}

#include <iostream>

int main() {
    int numbers[] = {1, 2, 3, 4, 5};
    int search = 4;
    int position = -1;

    for (int i = 0; i < 5; i++) {
        if (numbers[i] == search) {
            position = i;
            break;
        }
    }

    if (position != -1) {
        std::cout << "The number " << search << " is located at position " << position << std::endl;
    } else {
        std::cout << "The number " << search << " is not found in the array" << std::endl;
    }

    return 0;
}

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