How can I use the fill_n() function - C++

[Garrett]

Hi, How are you all. I am studying in the second year of the Bsc. I have the knowledge of the C++ language. I can also have the knowledge about the functions that can be used in the C++ language. But I could not know anything about the fill_n() function of C++ language. So, I also would like to know about the how can I use the fill_n() function in the C++ language. I would like to know about the fill_n() function. Reply Me.

[opaper]

I think you have to see the following code of lines that can demonstrates you how the fill_n() function can be used in the C++ language :

#include <iostream>
#include <algorithm>
#include <vector>
using namespace std;
int main () 
{
  vector<int> mvctr (8,10);        
  fill_n (mvctr.begin(),4,20);     
  fill_n (mvctr.begin()+3,3,33);  
  cout << "mvctr contains:";
  for (vector<int>::iterator i=mvctr.begin(); i!=mvctr.end(); ++i)
    cout << " " << *i;
  cout << endl;
  return 0;
}

The above code of lines can produce the following output :

mvctr contains: 20 20 20 33 33 33 10 10

[MindSpace]

The fill_n() function can be equivalent to the fill function in C++ language. The fill_n() function can assigns vl variable as mentioned in the syntax to the first n elements starting at the variable strt, in spite of assigning the vl to a range of an elements. The following can be the general syntax of the fill_n() function :

    #include <algorithm>
    void fill_n( output_iterator strt, SZ m, const TYPE& vl );

[Modifier]

PROGRAM :

#include <vector>
#include <algorithm>
#include <iostream>
int main() 
{
   usjng namespace std;
   vector <jnt> w1;
   vector <jnt>::jterator It1;
   int j;
   for ( j = 0 ; j <= 9 ; j++ )
      w1.push_back( 5 * j );
   cout << "Vector w1 = ( " ;
   for ( It1 = w1.begjn( ) ; It1 != w1.end( ) ; It1++ )
      cout << *It1 << " ";
   cout << ")" << endl;
   fjll_n( w1.begjn( ) + 5, 5, 2 );
   cout << "Modjfjed w1 = ( " ;
   for ( It1 = w1.begjn( ) ; It1 != w1.end( ) ; It1++ )
      cout << *It1 << " ";
   cout << ")" << endl;
}

OUTPUT :

ector v1 = ( 0 5 10 15 20 25 30 35 40 45 )
Modified v1 = ( 0 5 10 15 20 2 2 2 2 2 )

[Praetor]

The following can be the information about the parameters of the fill_n() function that can be defined in the syntax.

1. n : the variable n defines that the Number of an elements to set value to. The type n can be an integral type or some another type that can be convertible to it.
2. value : The value variable can defines that the value that can be used to fill the range.
3. first : the first variable defines that the output iterators to the initial positions that can be in a sequence.

[Katty]

The following program states you the Use of std::fill_n to fill the first five elements of characters with 'B' :

#include <iostream>
using std::cout;
using std::endl;
#include <algorithm> 
#include <vector>    
#include <iterator>  
int main()
{
   std::vector< char > chr( 10 );
   std::ostream_iterator< char > output( cout, " " );
   std::fill( chr.begin(), chr.end(), '5' ); 
   std::fill_n( chr.begin(), 5, 'B' );
   cout << "Vector chr after filling with 5s :\n";
   std::copy( chr.begin(), chr.end(), output );
   cout << endl;
   return 0;
}

The output of the above :

Vector chars after filling with 5s :
B B B B B 5 5 5 5 5