STD Library in C++

The most explicit and safe way is to always prefix std:: to each element,

#include <iostream>
#include <vector>

int main() {
    std::vector<int> numbers = {1, 2, 3};
    std::cout << "Example with explicit std:::" << std::endl;
    for (std::size_t i = 0; i < numbers.size(); ++i) {
        std::cout << numbers[i] << " ";
    }
    return 0;
}

This avoids name conflicts if your project or an external library defines something similar.

Another option is to use the statement using namespace std;, which eliminates the need to write std:: repeatedly

#include <iostream>
#include <vector>

using namespace std;

int main() {
    vector<int> numbers = {1, 2, 3};
    cout << "Example with using namespace std:" << endl;
    
    for (size_t i = 0; i < numbers.size(); ++i) {
        cout << numbers[i] << " ";
    }
    return 0;
}

But it can cause problems in large projects by introducing unnecessary names into the global namespace.

An intermediate alternative is to specifically declare the tools you use,

#include <iostream>
#include <vector>

using std::cout;
using std::endl;
using std::vector;

int main() {
    vector<int> numbers = {1, 2, 3};
    
    cout << "Example with specific using:" << endl;
    for (size_t i = 0; i < numbers.size(); ++i) {
        cout << numbers[i] << " ";
    }
    return 0;
}

This last option is preferable if you are working in small or well-defined files, as it maintains a good balance between clarity and convenience.

• std::cin: Object for standard input (keyboard).
• std::cout: Object for standard output (screen).
• std::cerr: Object for error output.
• std::clog: Object for logging messages output.

• std::ifstream: For reading data from files.
• std::ofstream: For writing data to files.
• std::fstream: For reading and writing files.

• std::vector: A container that stores elements in a dynamic array. Allows quick access to elements and dynamic resizing.
• std::list: A container that implements a doubly linked list, ideal for fast insertions and deletions anywhere in the list.
• std::deque: A double-ended container that allows efficient access at both ends of the container.

• std::set: Stores unique elements in a self-balancing binary tree. Allows for fast searches.
• std::map: Stores unique key-value pairs. Similar to std::set, but with key-value associations.
• std::unordered_set and std::unordered_map: Hash table-based implementations that provide average constant time access for search, insertion, and deletion operations.

• std::stack: A stack data structure that follows the LIFO (Last In, First Out) principle.
• std::queue: A queue data structure that follows the FIFO (First In, First Out) principle.
• std::priority_queue: A priority queue that stores elements in such a way that the highest priority element is extracted first.

• std::sort: Sorts the elements in a defined range. Uses an efficient sorting algorithm based on Quicksort.
• std::stable_sort: Sorts elements while maintaining the relative order of equivalent elements.

• std::find: Searches for an element in a range. Returns an iterator to the first found element or the end of the range if not found.
• std::binary_search: Searches for an element in a sorted range.

• std::transform: Applies a function to each element in a range and stores the result in another range.
• std::accumulate: Accumulates values in a range using a binary operation.

• std::count: Counts the number of occurrences of a value in a range.
• std::all_of, std::any_of, std::none_of: Evaluates whether all, any, or none of the elements in a range meet a condition.

• std::string: A class that facilitates the handling of text strings, providing a series of methods to manipulate and query strings efficiently.

• std::pair: A data structure that stores two values of possibly different types. Often used to return multiple values from a function.
• std::tuple: Similar to std::pair, but allows storing a variable number of elements of different types.

• std::optional: Represents a value that may or may not be present. Used to indicate the absence of a value without using pointers.

• std::variant: Allows storing one of several data types. It is a safe alternative to type pointers and is used to represent values that can be of different types.