Introduction to the Standard Template Library (STL)

The Standard Template Library (STL) is one of the most powerful components of C++. It provides a collection of template classes to manage data structures and generic algorithms, improving code efficiency and readability.

In this article, we will explore the key elements of STL with practical examples to help junior programmers understand its usage and advantages.

1. Why use STL?

Using STL offers several advantages:

• Efficient data management: Thanks to predefined containers, there is no need to implement complex data structures from scratch.
• Optimized performance: STL algorithms are highly optimized and leverage advanced techniques to ensure speed and efficiency.
• Code portability and maintenance: Code that uses STL is more readable and maintainable.
• Flexibility: Iterators allow traversing containers without worrying about the internal implementation of the data structure.

2. Main components of STL

STL is divided into three main components:

1. Containers: Data structures such as vector, list, map, set, etc.
2. Algorithms: Functions for common operations such as searching, sorting, and modifying.
3. Iterators: Objects that allow traversing containers in a uniform and efficient manner.

2.1 STL Containers

STL containers are divided into three categories:

• Sequence Containers: vector, list, deque.
• Associative Containers: set, map, multiset, multimap.
• Unordered Containers: unordered_set, unordered_map, unordered_multiset, unordered_multimap.

Let’s see some examples.

Vector

std::vector is a dynamic array that automatically grows.

#include <iostream>
#include <vector>

int main() {
    std::vector<int> vec = {1, 2, 3, 4, 5};
    vec.push_back(6);

    for (int val : vec) {
        std::cout << val << " ";
    }
    return 0;
}

List

std::list is a doubly linked list.

#include <iostream>
#include <list>

int main() {
    std::list<int> lst = {10, 20, 30};
    lst.push_front(5);
    lst.push_back(40);

    for (int val : lst) {
        std::cout << val << " ";
    }
    return 0;
}

Map

std::map is an ordered dictionary based on balanced trees.

#include <iostream>
#include <map>

int main() {
    std::map<std::string, int> age;
    age["Alice"] = 25;
    age["Bob"] = 30;

    for (const auto& p : age) {
        std::cout << p.first << ": " << p.second << std::endl;
    }
    return 0;
}

2.2 STL Algorithms

STL includes numerous algorithms for performing operations on containers.

Sorting with std::sort

#include <iostream>
#include <vector>
#include <algorithm>

int main() {
    std::vector<int> numbers = {5, 2, 9, 1, 5, 6};
    std::sort(numbers.begin(), numbers.end());

    for (int n : numbers) {
        std::cout << n << " ";
    }
    return 0;
}

Searching with std::find

#include <iostream>
#include <vector>
#include <algorithm>

int main() {
    std::vector<int> numbers = {1, 2, 3, 4, 5};
    auto it = std::find(numbers.begin(), numbers.end(), 3);
    
    if (it != numbers.end()) {
        std::cout << "Element found: " << *it << std::endl;
    } else {
        std::cout << "Element not found" << std::endl;
    }
    return 0;
}

2.3 Iterators

Iterators allow traversing containers uniformly and efficiently.

One of the main advantages of iterators is their efficiency compared to traditional indices. They enable iteration over any STL container without needing to know its internal implementation details.

#include <iostream>
#include <vector>

int main() {
    std::vector<int> numbers = {10, 20, 30, 40};
    std::vector<int>::iterator it;
    
    for (it = numbers.begin(); it != numbers.end(); ++it) {
        std::cout << *it << " ";
    }
    return 0;
}

3. Conclusion

STL is a powerful tool that simplifies the management of data structures and algorithms in C++. Understanding containers, algorithms, and iterators will improve code quality and development productivity.

A programmer should learn to use STL to:

• Write cleaner and more maintainable code.
• Reduce development time thanks to predefined and optimized solutions.
• Improve software performance with efficient algorithms and suitable data structures.

We encourage you to experiment with the provided examples and explore other STL functionalities to enhance your mastery of C++!