Arrays & Introduction to Vectors

⚡ C++ Lesson 7 Intermediate

C++ supports fixed-size contiguous memory arrays, as well as dynamic STL vectors that resize automatically.

1 Fixed Arrays vs. Dynamic STL Vectors

Standard arrays are fixed in size at compilation time, and C++ does not perform out-of-bounds safety checks. To prevent buffer overflows, C++'s Standard Template Library (STL) provides **`std::vector`**, which manages memory dynamically on the heap and resizes as elements are added.

2 Vector & Matrix operations

Let's run a program defining static matrices and dynamic vectors, adding and accessing elements safely:

C++ — Arrays and Vectors ▶ Run Code

#include <iostream>
#include <vector> // Needed for std::vector

int main() {
    // 1. Fixed-size array matrix
    int matrix[2][3] = {
        {1, 2, 3},
        {4, 5, 6}
    };
    
    std::cout << "Matrix element [1][2]: " << matrix[1][2] << "\n";

    // 2. Dynamic Vector
    std::vector<int> numbers;
    numbers.push_back(10); // Add elements dynamically
    numbers.push_back(20);
    numbers.push_back(30);

    std::cout << "Vector Size: " << numbers.size() << "\n";
    std::cout << "Vector elements: ";
    for (int n : numbers) { // Modern range-based for loop
        std::cout << n << " ";
    }
    std::cout << "\n";

    return 0;
}

3 Code Challenge

Challenge: Write a program that declares a `std::vector` of doubles. Use a loop to populate it with the squares of numbers from 1.0 to 5.0. Output the size of the vector and iterate through it to print the values.