CodeCogs

Replaces n elements with a given value

Definition

The fill_n() algorithm is defined in the standard header <algorithm> and in the nonstandard backward-compatibility header <algo.h>.

Interface

#include <algorithm>
template < class OutputIterator, class Size, class Type >
   void fill_n(
      OutputIterator first, 
      Size count, 
      const Type& val
   );

Parameters:

Parameter	Description
first	An output iterator addressing the position of the first element in the range to be assigned the value `val`
count	A signed or unsigned integer type specifying the number of elements to be assigned the value
val	The value to be assigned to elements in the range `[first, first + count)`

Description

Fill_n algorithm does the same thing that http://www.codecogs.com/reference/computing/stl/algorithms/modifying/fill.php"fill" but fills n elements.

Return Value

None.

Complexity

The complexity is linear; performs n assignments.

References

http://msdn.microsoft.com/en-us/

Example 1

Problem

The following program demonstrates how to use fill_n() function.

Workings

#include <vector>
#include <algorithm>
#include <iostream>

using namespace std;
 
int main()
{
  vector <int> vec;
  vector <int>::iterator Iter1;
  int i;
  for (i = 10; i <= 20; i++)
    vec.push_back(i);
  cout <<"Vector vec data: ";
  for (Iter1 = vec.begin(); Iter1 != vec.end(); Iter1++)
    cout <<*Iter1<<" ";
  cout <<endl;
  // fill the last 3 positions for 6 position with a value of 9
  cout <<"\nOperation: fill_n(vec.begin() + 3, 6, 9)\n";
  fill_n(vec.begin() + 3, 6, 9);
  cout <<"Modified vec data: ";
  for (Iter1 = vec.begin(); Iter1 != vec.end(); Iter1++)
    cout <<*Iter1<<" ";
   cout <<endl;

  return 0;
}

Solution

Output:

Vector vec data: 10 11 12 13 14 15 16 17 18 19 20
Operation: fill_n(vec.begin() + 3, 6, 9)
Modified vec data: 10 11 12 9 9 9 9 9 9 19 20

References

http://www.tenouk.com/

Example 2

Problem

This program illustrates the use of the STL fill_n() algorithm to set a given number values starting at a given location in a vector of integers to a given value.

Workings

#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

int main()
{
  int a[] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
  vector<int> v(a, a+10);
  cout <<"\nHere are the contents of v:\n";
  for (vector<int>::size_type i=0; i<v.size(); i++)
    cout <<v.at(i)<<" ";

  cout <<"\nNow we set 5 values of v, starting at the 3rd, to 50.";
  fill_n(v.begin()+2, 5, 50);
  cout <<"\nHere are the revised contents of v:\n";
  for (vector<int>::size_type i=0; i<v.size(); i++)
    cout <<v.at(i)<<" ";

  cout <<"\nNow we set the last three values of v to -1.";
  fill_n(v.begin()+7, 3, -1);
  cout <<"\nHere are the revised contents of v:\n";
  for (vector<int>::size_type i=0; i<v.size(); i++)
    cout <<v.at(i)<<" ";

  cout <<"\nFinally, we initialize the entire vector to 100.";
  fill_n(v.begin(), v.size(), 100);
  cout <<"\nHere are the revised contents of v:\n";
  for (vector<int>::size_type i=0; i<v.size(); i++)
    cout <<v.at(i)<<" ";

  return 0;
}

Solution

Output:

Here are the contents of v:
1 2 3 4 5 6 7 8 9 10

Now we set 5 values of v, starting at the 3rd, to 50.
Here are the revised contents of v:
1 2 50 50 50 50 50 8 9 10

Now we set the last three values of v to -1.
Here are the revised contents of v:
1 2 50 50 50 50 50 -1 -1 -1

Finally, we initialize the entire vector to 100.
Here are the revised contents of v:
100 100 100 100 100 100 100 100 100 100

References

http://www.smu.ca/academic/science/compsci/

fill_n

Definition

Interface

Description

Return Value

Complexity

References

Example 1

Example 2

See Also