fill_n

  #include <algorithm>
  #include <algorithm>
  iterator fill_n( iterator start, size_t n, const TYPE& val );

The fill_n() function is similar to (C++ I/O) fill(). Instead of assigning val to a range of elements, however, fill_n() assigns val to the first n elements starting at start.

For example, the following code uses fill_n() to assign -1 to the first half of a vector of integers:

 vector<int> v1;
 for( int i = 0; i < 10; i++ ) {
   v1.push_back( i );
 }              

 cout << "Before, v1 is: ";
 for( unsigned int i = 0; i < v1.size(); i++ ) {
   cout << v1[i] << " ";
 }
 cout << endl;            

 fill_n( v1.begin(), v1.size()/2, -1 );         

 cout << "After, v1 is: ";
 for( unsigned int i = 0; i < v1.size(); i++ ) {
   cout << v1[i] << " ";
 }
 cout << endl;            

When run, this code displays:

 Before, v1 is: 0 1 2 3 4 5 6 7 8 9
 After, v1 is: -1 -1 -1 -1 -1 5 6 7 8 9