C++ set begin() Function

by Online Tutorials Library July 22, 2022

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

begin()beginners c cbegin()cend()clear()constructor cpp set crbegin()destructor emplace_hint()empty end()function introduction key_comp()max_size()operator professionals swap()tutorial

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

What is boot

C++ Math scalbln() Function

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