**Sets** are associative containers that store *unique* elements. A stored element must be unique because it is identified with the value itself. Once the elements are inserted in the set, they cannot be modified; however, they *can* be inserted or removed from the container. 

# Set methods

Below are some of the basic methods associated with sets:

- **`begin()`** returns an iterator to the first element in a set.

- **`end()`** returns an iterator to the "theoretical" element that is after the last element in a set.

- **`insert(const val)`** adds a new element (`val`) to a set.

- **`erase(const val)`** removes the element (`val`) from a set.

- **`clear()`** removes all the elements from a set.

- **`size()`** returns the number of elements in a​ set.

# Code

The code snippet below illustrates how the functions above are used​:

#include <iostream>
#include <set>
using namespace std;

int main() {
  // Declaring a set
  set<string> Fruits;

  // using insert method to add elements to the set
  Fruits.insert("Apple");
  Fruits.insert("Banana");
  Fruits.insert("Kiwi");

  // using begin and end to iterate through the set
  cout << "Elements of the set:       ";
  for(std::set<string>::iterator i = Fruits.begin(); i != Fruits.end(); i++)
  {
    cout << *i << ", ";
  }
  cout << endl;
  cout << endl;


  // using remove method to remove elemets from the set
  Fruits.erase("Apple");

  cout << "After removing Apple:   ";
  for(std::set<string>::iterator i = Fruits.begin(); i != Fruits.end(); i++)
  {
    cout << *i << ", ";
  }
  cout << endl;
  cout << endl;


  // Checking for number eof elements in the set
  cout << "Fruits has " << Fruits.size() << " elements" << endl;

  cout << endl;

  // clearing the set
  Fruits.clear();

  cout << "Fruits now has " << Fruits.size() << " elements" << endl;

  return 0;
}

Sets in C++

Sets in C++ are containers storing unique elements, with methods to add, remove, and iterate elements.