C++ Tutorial/STL Algorithms Modifying sequence operations/fill n

Use fill_n function to insert "hello" nine times

<source lang="cpp">/* The following code example is taken from the book

* "The C++ Standard Library - A Tutorial and Reference"
* by Nicolai M. Josuttis, Addison-Wesley, 1999
*
* (C) Copyright Nicolai M. Josuttis 1999.
* Permission to copy, use, modify, sell and distribute this software
* is granted provided this copyright notice appears in all copies.
* This software is provided "as is" without express or implied
* warranty, and with no claim as to its suitability for any purpose.
*/

1. include <iostream>
2. include <vector>
3. include <deque>
4. include <list>
5. include <set>
6. include <map>
7. include <string>
8. include <algorithm>
9. include <iterator>
10. include <functional>
11. include <numeric>

/* PRINT_ELEMENTS()

* - prints optional C-string optcstr followed by
* - all elements of the collection coll
* - separated by spaces
*/

template <class T> inline void PRINT_ELEMENTS (const T& coll, const char* optcstr="") {

   typename T::const_iterator pos;
   std::cout << optcstr;
   for (pos=coll.begin(); pos!=coll.end(); ++pos) {
       std::cout << *pos << " ";
   }
   std::cout << std::endl;

} /* INSERT_ELEMENTS (collection, first, last)

* - fill values from first to last into the collection
* - NOTE: NO half-open range
*/

template <class T> inline void INSERT_ELEMENTS (T& coll, int first, int last) {

   for (int i=first; i<=last; ++i) {
       coll.insert(coll.end(),i);
   }

}

using namespace std; int main() {

   // print ten times 7.7
   fill_n(ostream_iterator<float>(cout, " "), // beginning of destination
          10,                                 // count
          7.7);                               // new value
   cout << endl;
   list<string> coll;
   // insert "hello" nine times
   fill_n(back_inserter(coll),       // beginning of destination
          9,                         // count
          "hello");                  // new value
   PRINT_ELEMENTS(coll,"coll: ");

}</source>

7.7 7.7 7.7 7.7 7.7 7.7 7.7 7.7 7.7 7.7
coll: hello hello hello hello hello hello hello hello hello

Use fill_n function to replace all but two elements with "hi"

<source lang="cpp">/* The following code example is taken from the book

* "The C++ Standard Library - A Tutorial and Reference"
* by Nicolai M. Josuttis, Addison-Wesley, 1999
*
* (C) Copyright Nicolai M. Josuttis 1999.
* Permission to copy, use, modify, sell and distribute this software
* is granted provided this copyright notice appears in all copies.
* This software is provided "as is" without express or implied
* warranty, and with no claim as to its suitability for any purpose.
*/

1. include <iostream>
2. include <vector>
3. include <deque>
4. include <list>
5. include <set>
6. include <map>
7. include <string>
8. include <algorithm>
9. include <iterator>
10. include <functional>
11. include <numeric>

/* PRINT_ELEMENTS()

* - prints optional C-string optcstr followed by
* - all elements of the collection coll
* - separated by spaces
*/

template <class T> inline void PRINT_ELEMENTS (const T& coll, const char* optcstr="") {

   typename T::const_iterator pos;
   std::cout << optcstr;
   for (pos=coll.begin(); pos!=coll.end(); ++pos) {
       std::cout << *pos << " ";
   }
   std::cout << std::endl;

} /* INSERT_ELEMENTS (collection, first, last)

* - fill values from first to last into the collection
* - NOTE: NO half-open range
*/

template <class T> inline void INSERT_ELEMENTS (T& coll, int first, int last) {

   for (int i=first; i<=last; ++i) {
       coll.insert(coll.end(),i);
   }

}

using namespace std; int main() {

   // print ten times 7.7
   fill_n(ostream_iterator<float>(cout, " "), // beginning of destination
          10,                                 // count
          7.7);                               // new value
   cout << endl;
   list<string> coll;
   // insert "hello" nine times
   fill_n(back_inserter(coll),       // beginning of destination
          9,                         // count
          "hello");                  // new value
   // replace all but two elements with "hi"
   fill_n(coll.begin(),              // beginning of destination
          coll.size()-2,             // count
          "hi");                     // new value
   PRINT_ELEMENTS(coll,"coll: ");

}</source>

7.7 7.7 7.7 7.7 7.7 7.7 7.7 7.7 7.7 7.7
coll: hi hi hi hi hi hi hi hello hello

Use fill_n to Fill the three elements starting at offset position 3 with value -9

<source lang="cpp">#include <algorithm>

1. include <vector>
2. include <iostream>

using namespace std; int main () {

   vector <int> v (3);
   v.resize (6);
   // Fill the three elements starting at offset position 3 with value -9
   fill_n (v.begin () + 3, 3, -9);
   cout << "Contents of the vector are: " << endl;
   for (size_t nIndex = 0; nIndex < v.size (); ++ nIndex){
       cout << "Element [" << nIndex << "] = ";
       cout << v [nIndex] << endl;
   }
   return 0;

}</source>

Use std::fill_n to fill the first five elements of chars with "A"

<source lang="cpp">#include <iostream> using std::cout; using std::endl;

1. include <algorithm> // algorithm definitions
2. include <vector> // vector class-template definition
3. include <iterator> // ostream_iterator

int main() {

  std::vector< char > chars( 10 );
  std::ostream_iterator< char > output( cout, " " );
  std::fill( chars.begin(), chars.end(), "5" ); // fill chars with 5s
 // fill first five elements of chars with As
  std::fill_n( chars.begin(), 5, "A" );

  cout << "Vector chars after filling with 5s:\n";
  std::copy( chars.begin(), chars.end(), output );
  cout << endl;
  return 0;

}</source>

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

Use the fill_n algorithms: Fill 3 more positions with Y"s

<source lang="cpp">#include <iostream>

1. include <cassert>
2. include <algorithm>
3. include <vector>
4. include <string>

using namespace std; int main() {

 string s("Hello there");
 vector<char> vector1(s.begin(), s.end());

 fill_n(vector1.begin() + 5, 3, "Y");
 vector<char>::iterator pos;
 for (pos=vector1.begin(); pos!=vector1.end(); ++pos) {
       cout << *pos << " ";
 }

 return 0;

}</source>

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