Introduction to STL

What is STL?

The Standard Template Library (STL) is a powerful set of C++ template classes to provide general-purpose classes and functions with templates that implement many popular and commonly used algorithms and data structures like vectors, lists, queues, and stacks. STL has four components:

• Algorithms
• Containers
• Functions
• Iterators

Containers

Containers are objects that store data. STL provides several types of containers:

• Sequence Containers: These store data in a linear sequence. Examples include vector, deque, list.
• Associative Containers: These store data in a sorted order. Examples include set, map, multiset, multimap.
• Derived Containers: These are containers with real-world modeling. Examples include stack, queue, priority_queue.

Iterators

Iterators are used to point at the memory addresses of STL containers. They are used to iterate over container elements. Some important iterator types include:

• Input Iterators: Used to read values from a sequence.
• Output Iterators: Used to write values to a sequence.
• Forward Iterators: Can be read and written to in a forward direction.
• Bidirectional Iterators: Can be read and written to in both forward and backward directions.
• Random Access Iterators: Can be read and written to and can jump to any element.

Algorithms

Algorithms are a set of instructions applied to the data structures to perform operations like searching, sorting, etc. STL provides many algorithms, such as:

• sort
• reverse
• copy
• find
• binary_search

Example: Using a Vector

Below is an example of how to use a vector in C++:

#include <iostream>
#include <vector>

int main() {
    std::vector<int> vec;

    // Adding elements to vector
    vec.push_back(1);
    vec.push_back(2);
    vec.push_back(3);

    // Displaying elements of vector
    for(int i = 0; i < vec.size(); i++) {
        std::cout << vec[i] << " ";
    }
    return 0;
}
                

Example: Using a Map

Below is an example of how to use a map in C++:

#include <iostream>
#include <map>

int main() {
    std::map<std::string, int> map;

    // Adding elements to map
    map["one"] = 1;
    map["two"] = 2;
    map["three"] = 3;

    // Displaying elements of map
    for(const auto &pair : map) {
        std::cout << pair.first << ": " << pair.second << std::endl;
    }
    return 0;
}