C++ set - begin() Function

The C++ set::begin function returns the iterator pointing to the first element of the set. Please note that, Set is an ordered data container which implies all its elements are ordered all the time.

Syntax

C++98
C++11

iterator begin();
const_iterator begin() const;

iterator begin() noexcept;
const_iterator begin() const noexcept;

Parameters

No parameter is required.

Return Value

An iterator to the beginning of the sequence container. If the sequence object is constant qualified, the function returns a const_iterator, else returns an iterator.

Time Complexity

Constant i.e, Θ(1).

Example:

In the example below, the set::begin function returns the iterator pointing to the first element of the set called MySet.

#include <iostream>
#include <set>
using namespace std;
 
int main (){
  set<string> MySet{"Alpha","Coding","Skills"};
  set<string>::iterator it;

  it = MySet.begin();
  cout<<*it<<" ";
  it++;
  cout<<*it<<" ";
  it++;
  cout<<*it<<" ";
  return 0;
}

The output of the above code will be:

Alpha Coding Skills

Example:

Lets see another example where the set called MySet contains integer values and set::begin function is used with set::end function to specify a range including all elements of the set container. Please note that, Set is an ordered data container.

#include <iostream>
#include <set>
using namespace std;
 
int main (){
  set<int> MySet{55, 25, 128, 5, 72};
  set<int>::iterator it;

  for(it = MySet.begin(); it != MySet.end(); ++it)
    cout<<*it<<" ";

  return 0;
}

The output of the above code will be:

5 25 55 72 128

❮ C++ <set> Library