C++ multiset begin
The begin function in C++ multiset is utilized to retrieve an iterator pointing to the initial element within the multiset 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
Return value
It yields an iterator referencing the initial element of the multiset.
Complexity
Constant.
Iterator validity
No changes.
Data Races
The container is retrieved. Both the constant and non-constant variations do not alter the container.
Exception Safety
This function never throws exceptions.
Example 1
Let's explore a basic illustration showcasing the functionality of the begin method:
#include <iostream>
#include <set>
using namespace std;
int main ()
{
multiset<string> mymultiset= {"Java", "C++", "SQL","C++"};
// show content:
cout<<"Contents of mymultiset are: "<<endl;
for (multiset<string>::iterator it=mymultiset.begin(); it!=mymultiset.end(); ++it)
cout << *it<< '\n';
return 0;
}
Output:
Contents of mymultiset are:
C++
C++
Java
SQL
The begin method is employed to retrieve an iterator that points to the initial element within the mymultiset multiset.
Example 2
Let's see a simple example:
#include <iostream>
#include <set>
using namespace std;
int main()
{
multiset<int> c;
c.insert(5);
c.insert(2);
c.insert(4);
c.insert(2);
c.insert(0);
c.insert(5);
multiset<int>::iterator i = c.begin();
while (i != c.end())
cout << *i++ << " ";
cout << endl;
}
Output:
0 2 2 4 5 5
Example 3
Let's examine a basic illustration of iterating through the multiset utilizing a while loop:
#include <iostream>
#include <set>
#include <string>
int main()
{
using namespace std;
multiset<string> mymultiset = { "Nikita","Deep","Priya","Suman","Aman","Nikita" };
cout<<"Elements of mymultiset are: "<<endl;
multiset<string>::const_iterator it; // declare an iterator
it = mymultiset.begin(); // assign it to the start of the multiset
while (it != mymultiset.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 mymultiset are:
Aman
Deep
Nikita
Nikita
Priya
Suman
The start method is employed to retrieve an iterator that points to the initial element within the mymultiset multiset.
Example 4
Let's see a simple example:
#include <set>
#include <iostream>
int main( )
{
using namespace std;
multiset <int> s1;
multiset <int>::iterator s1_Iter;
s1.insert( 1 );
s1.insert( 2 );
s1.insert( 3 );
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
The begin method is employed to retrieve an iterator that points to the initial element within the mymultiset multiset.
