C++ set begin() Function

C++ set begin() Function with tutorial for beginners and professionals with examples on constructor, destructor, operator=(), begin(), cbegin(), cend(), end(), crbegin(), empty(), max_size(), clear(), emplace_hint(), key_comp(), swap() etc.

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C++ set begin()

C++ set begin() function is used to return an iterator referring to the first element of the set container.

Syntax

      iterator begin();                            //until C++ 11
const_iterator begin() const;                //until C++ 11
      iterator begin() noexcept;              //since C++ 11
const_iterator begin() const noexcept;  //since C++ 11

Parameter

None

Return value

It returns an iterator pointing to the first element of the set.

Complexity

Constant.

Iterator validity

No changes.

Data Races

The container is accessed. Neither the constant nor the non-constant versions modify the container.

Exception Safety

This function never throws exceptions.

Example 1

Let's see the simple example for begin() function:

#include <iostream>
#include <set>

using namespace std;

int main ()
{
  set<string> myset= {"Java", "C++", "SQL"};

  // show content:
  cout<<"Contents of myset are: "<<endl;
  for (set<string>::iterator it=myset.begin(); it!=myset.end(); ++it)
    cout << *it<< '\n';

  return 0;
}

Output:

Contents of myset are: 
C++
Java
SQL

In the above example, begin() function is used to return an iterator pointing to the first element in the myset set.

Example 2

Let's see a simple example:

#include <iostream>
#include <set>

using namespace std;

int main()
{
  set<int> c;
  c.insert(5);
  c.insert(2);
  c.insert(4);
  c.insert(1);
  c.insert(0);
  c.insert(9);

  set<int>::iterator i = c.begin();
  while (i != c.end())
  cout << *i++ << " ";
  cout << endl;
}

Output:

0 1 2 4 5 9

Example 3

Let's see a simple example to iterate over the set using while loop:

#include <iostream>
#include <set>
#include <string>
int main()
{
    using namespace std;
 
      set<string> myset = { "Nikita","Deep","Priya","Suman","Aman" };

 cout<<"Elements of myset are: "<<endl;
    set<string>::const_iterator it; // declare an iterator

    it = myset.begin(); // assign it to the start of the set

    while (it != myset.end()) // while it hasn't reach the end
    {
cout << *it << "\n"; 

// print the value of the element it points to

++it; // and iterate to the next element
    }
 
    cout << endl;
}

Output:

Elements of myset are: 
Aman
Deep
Nikita
Priya
Suman

In the above, begin() function is used to return an iterator pointing to the first element in the myset set.

Example 4

Let's see a simple example:

#include <set>  
#include <iostream>  
  
int main( )  
{  
   using namespace std;  
   set <int> s1;  
   set <int>::iterator s1_Iter;    
  
   s1.insert( 1 );  
   s1.insert( 2 );  
   s1.insert( 3 );  
  
   s1_Iter = s1.begin( );  
   cout << "The first element of s1 is " << *s1_Iter << endl;  
  
   s1_Iter = s1.begin( );  
   s1.erase( s1_Iter );  

   s1_Iter = s1.begin( );  
   cout << "The first element of s1 is now " << *s1_Iter << endl;  
}

Output:

The first element of s1 is 1
The first element of s1 is now 2

In the above example, begin() function is used to return an iterator pointing to the first element in the myset set.

Next TopicSet cbegin() Function

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C++ set begin() Function

C++ set begin()

Syntax

Parameter

Return value

Complexity

Iterator validity

Data Races

Exception Safety

Example 1

Example 2

Example 3

Example 4

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