C++ Vector: Dynamic Arrays with STL

In C++, the 'std::vector' class is a dynamic array that can be resized at runtime. It's part of the Standard Template Library (STL) and offers a more flexible alternative to static arrays.

Here's an example demonstrating how to use 'std::vector' in C++:

#include <iostream>
#include <vector>

int main() {
    // Create an empty vector
    std::vector<int> numbers;

    // Add elements to the vector
    numbers.push_back(10);
    numbers.push_back(20);
    numbers.push_back(30);

    // Access elements using indexing
    std::cout << numbers[0] << std::endl;  // Output: 10

    // Access elements using iterator
    for (std::vector<int>::iterator it = numbers.begin(); it != numbers.end(); ++it) {
        std::cout << *it << " ";
    }
    std::cout << std::endl;  // Output: 10 20 30

    // Get the size of the vector
    std::cout << "Size: " << numbers.size() << std::endl;  // Output: 3

    // Resize the vector
    numbers.resize(5, 50);  // Resize to 5 elements, with default value 50

    // Print the vector after resizing
    for (int i = 0; i < numbers.size(); i++) {
        std::cout << numbers[i] << " ";
    }
    std::cout << std::endl;  // Output: 10 20 30 50 50

    return 0;
}

In this example, we create a vector named 'numbers' and add elements using the 'push_back' function. Elements can be accessed through indexing or iterators. The 'size' function returns the vector's element count. We can also resize the vector using the 'resize' function, which allows modifying the size and optionally setting a default value for new elements.