Cpp2_2.html

<article>
    <h1>C++ II: Page 2 - STL: Maps & Sets</h1>

    <section>
        <h2>Associative Containers</h2>
        <p>Associative containers in the STL, such as <code>std::map</code> and <code>std::set</code>, are designed for fast lookup, insertion, and deletion of elements. Maps store key-value pairs, while sets store unique keys.</p>
        
        <h3>The Code implementation</h3>
        <pre><code class="language-cpp">/*
 * File: associative.cpp
 * Demonstration of std::map, std::unordered_map, std::set, and std::multimap
 */
#include &lt;iostream&gt;
#include &lt;map&gt;
#include &lt;unordered_map&gt;
#include &lt;set&gt;
#include &lt;string&gt;

using namespace std;

int main() {
    // 1. std::map (Ordered key-value, balanced tree)
    map&lt;string, int&gt; phoneBook;
    phoneBook["Alice"] = 12345;
    phoneBook["Bob"] = 67890;
    
    // 2. std::unordered_map (Unordered key-value, hash table)
    unordered_map&lt;string, string&gt; capitalCities;
    capitalCities["France"] = "Paris";
    capitalCities["Japan"] = "Tokyo";
    
    // 3. std::set (Unique, ordered keys)
    set&lt;int&gt; uniqueIds = {1, 2, 3, 1, 2}; // 1 is stored once
    
    // 4. std::multimap (Multiple values for one key)
    multimap&lt;string, string&gt; userRoles;
    userRoles.insert({"Alice", "Admin"});
    userRoles.insert({"Alice", "Editor"});
    
    // 5. Lookup
    if (phoneBook.find("Alice") != phoneBook.end()) {
        cout << "Alice's number: " << phoneBook["Alice"] << endl;
    }
    
    // 6. Iteration (Structured binding C++17)
    cout << "Phonebook entries: " << endl;
    for (const auto& [name, number] : phoneBook) {
        cout << name << ": " << number << endl;
    }
    
    // 7. Erasing elements
    uniqueIds.erase(2);
    
    return 0;
}

/*
 * Associative Container Nuances:
 * 1. map: O(log n) access time, keys are sorted.
 * 2. unordered_map: O(1) average access time (hash table).
 * 3. set: O(log n) insertion/deletion, guarantees unique, sorted elements.
 * 4. multimap: Allows duplicate keys.
 * 5. Structured binding (C++17) simplifies map iteration (const auto& [key, val]).
 * 6. Prefer unordered_map unless ordering is explicitly required.
 * 7. Erasing elements from a map invalidates only iterators to the erased element.
 */
        </code></pre>
        <div class="interactive-sim">
            <h3>Map Simulator</h3>
            <button class="sim-button" onclick="
                const out = document.getElementById('sim-output-cpp2_2');
                out.innerHTML = 'map[&quot;Alice&quot;] = 123;<br>';
                setTimeout(() => out.innerHTML += '>> Alice number is ' + 123, 800);
            ">Run Simulation</button>
            <div id="sim-output-cpp2_2" class="sim-output"></div>
        </div>
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