C++ Tutorial/list/list remove

Good way and bad way to remove elements in a list

<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 <list>
3. include <algorithm>

using namespace std; int main() {

   list<int> coll;
   // insert elements from 6 to 1 and 1 to 6
   for (int i=1; i<=6; ++i) {
       coll.push_front(i);
       coll.push_back(i);
   }
   // remove all elements with value 3
   // - poor performance
   coll.erase (remove(coll.begin(),coll.end(),
                      3),
               coll.end());
   // remove all elements with value 4
   // - good performance
   coll.remove (4);

}</source>

Remove all elements with the same value

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

1. include <list> // list class-template definition
2. include <algorithm> // copy algorithm
3. include <iterator> // ostream_iterator

int main() {

  int array[ 4 ] = { 2, 6, 4, 8 };
  std::list< int > values;      // create list of ints
  std::list< int > otherValues; // create list of ints
  std::ostream_iterator< int > output( cout, " " );
  // insert items in values
  values.push_front( 1 );
  values.push_front( 3 );
  values.push_back( 4 );
  values.push_back( 1 );
  values.push_back( 2 );
  values.push_back( 3 );
  cout << "values contains: ";
  std::copy( values.begin(), values.end(), output );
  values.remove( 1 ); // remove all 1s
  cout << "\n\nvalues contains: ";
  std::copy( values.begin(), values.end(), output );
  cout << endl;
  return 0;

}</source>

values contains: 3 1 4 1 2 3
values contains: 3 4 2 3

Remove element from a list

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

1. include <list>

using namespace std; void show(const char *msg, list<char> lst); int main() {

 list<char> lstA;
 lstA.push_back("A");
 lstA.push_back("F");
 lstA.push_back("B");
 lstA.push_back("R");
 // Remove A and H.
 lstA.remove("A");
 lstA.remove("H");
 show("lstA after removing A and H: ", lstA);
 cout << endl;
 return 0;

} void show(const char *msg, list<char> lst) {

 list<char>::iterator itr;
 cout << msg << endl;
 for(itr = lst.begin(); itr != lst.end(); ++itr)
   cout << *itr << endl;

}</source>