C++ set begin
The begin function in C++ set is employed to retrieve an iterator pointing to the initial element within the set data structure.
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
Return value
It returns an iterator that references the initial element of the set.
Complexity
Constant.
Iterator validity
No changes.
Data Races
Accessing the container does not result in any modifications, regardless of whether the constant or non-constant versions are used.
Exception Safety
This function never throws exceptions.
Example 1
Let's explore a straightforward illustration showcasing the 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
The begin method is employed to retrieve an iterator that points to the initial element within 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 examine a basic illustration of iterating through a set using a 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 icpp tutorials to
++it; // and iterate to the next element
}
cout << endl;
}
Output:
Elements of myset are:
Aman
Deep
Nikita
Priya
Suman
The begin method is employed to retrieve an iterator that points to the initial element within 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 example provided, the begin method is employed to retrieve an iterator that points to the initial element within the myset set.
