Cpp2_1.html

<article>
    <h1>C++ II: Page 1 - STL: Vectors</h1>

    <section>
        <h2>Dynamic Arrays with std::vector</h2>
        <p>The <code>std::vector</code> is the workhorse of modern C++ containers. It manages dynamic arrays, automatically handling memory resizing as elements are added or removed.</p>
        
        <h3>The Code implementation</h3>
        <pre><code class="language-cpp">/*
 * File: vectors.cpp
 * Demonstration of std::vector functionality, including reserve and emplace_back
 */
#include &lt;iostream&gt;
#include &lt;vector&gt;
#include &lt;algorithm&gt;
#include &lt;string&gt;

using namespace std;

struct Data {
    int id;
    string name;
};

int main() {
    // 1. Creation and Initialization
    vector&lt;int&gt; numbers = {10, 20, 30};
    
    // 2. Optimization: reserve()
    // Pre-allocating memory avoids costly reallocations
    numbers.reserve(10);
    
    // 3. Dynamic resizing: emplace_back()
    // More efficient than push_back() for objects (constructs in place)
    numbers.push_back(40);
    numbers.push_back(50);
    
    // 4. Access
    cout << "First element: " << numbers[0] << endl;
    cout << "Size: " << numbers.size() << " | Capacity: " << numbers.capacity() << endl;
    
    // 5. Modification
    numbers.pop_back(); // Removes 50
    
    // 6. Iteration (Modern C++)
    cout << "All elements: ";
    for (const auto& n : numbers) {
        cout << n << " ";
    }
    cout << endl;

    // 7. Emplacing objects in vector
    vector&lt;Data&gt; dataItems;
    dataItems.emplace_back(Data{1, "Item1"});
    dataItems.emplace_back(1, "Item2"); // Direct construction
    
    // 8. Sorting
    sort(numbers.begin(), numbers.end(), greater&lt;int&gt;());
    
    cout << "Sorted (desc): ";
    for (int n : numbers) cout << n << " ";
    cout << endl;
    
    return 0;
}

/*
 * Vector Nuances:
 * 1. Vectors automatically manage heap memory.
 * 2. 'size()' returns current elements, 'capacity()' returns total space allocated.
 * 3. Vectors resize themselves when capacity is exceeded, which can be costly (O(n)).
 * 4. Use 'reserve()' if you know the final size to prevent multiple reallocations.
 * 5. Accessing out of bounds using '[]' causes undefined behavior; use '.at()' for safety.
 * 6. 'emplace_back()' constructs the object in place, avoiding a copy/move operation.
 */
        </code></pre>
        <div class="interactive-sim">
            <h3>Vector Simulator</h3>
            <button class="sim-button" onclick="
                const out = document.getElementById('sim-output-cpp2_1');
                out.innerHTML = 'vec = {10, 20};<br>';
                setTimeout(() => out.innerHTML += '>> vec.push_back(30);<br>>> Vector size is 3', 800);
            ">Run Simulation</button>
            <div id="sim-output-cpp2_1" class="sim-output"></div>
        </div>
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