C++ Tutorial/STL Algorithms Modifying sequence operations/remove copy

Copy from one vector to another and remove values with remove_copy()

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

1. include <algorithm>
2. include <vector>

using namespace std; bool greater9( int ); int main() {

  const int SIZE = 10;
  int a[ SIZE ] = { 10, 2, 10, 4, 16, 6, 14, 8, 12, 10 };
  // Remove 10 from v
  vector< int > v( a, a + SIZE );
  vector< int >::iterator newLastElement;
  newLastElement = remove( v.begin(), v.end(), 10 );
  // Copy from v2 to c, removing 10s
  vector< int > v2( a, a + SIZE );
  vector< int > c( SIZE, 0 );
  remove_copy( v2.begin(), v2.end(), c.begin(), 10 );
  return 0;

} bool greater9( int x ) {

  return x > 9;

}</source>

std::remove_copy

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

1. include <algorithm>
2. include <vector>
3. include <iterator>

int main() {

  int a[ 10 ] = { 10, 2, 10, 4, 16, 6, 14, 8, 12, 10 };
  std::ostream_iterator< int > output( cout, " " );
  std::vector< int > v2( a, a + 10 ); // copy of a
  std::vector< int > c( 10, 0 ); // instantiate vector c
  cout << "Vector v2 before removing all 10s and copying:\n   ";
  std::copy( v2.begin(), v2.end(), output );
  // copy from v2 to c, removing 10s in the process
  std::remove_copy( v2.begin(), v2.end(), c.begin(), 10 );
  cout << "\nVector c after removing all 10s from v2:\n   ";
  std::copy( c.begin(), c.end(), output );
  return 0;

}</source>

Vector v2 before removing all 10s and copying:
   10 2 10 4 16 6 14 8 12 10
Vector c after removing all 10s from v2:
   2 4 16 6 14 8 12 0 0 0

Use remove_copy to delete all space in a char array

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

1. include <vector>
2. include <algorithm>

using namespace std;

int main() {

 char str[] = "This is a test.";
 vector<char> v, v2(30);
 unsigned int i;
  
 for(i=0; str[i]; i++) v.push_back(str[i]);
  
 for(i=0; i<v.size(); i++) cout << v[i];
  
 // remove all spaces
 remove_copy(v.begin(), v.end(), v2.begin(), " ");
  
 cout << "Result after removing spaces:\n";
 for(i=0; i<v2.size(); i++) cout << v2[i];
 cout << endl << endl;
  
 return 0;

}</source>

Use remove_copy to print elements without those having the value 3

<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() {

   list<int> coll1;
   INSERT_ELEMENTS(coll1,1,6);
   INSERT_ELEMENTS(coll1,1,9);
   PRINT_ELEMENTS(coll1);
   // print elements without those having the value 3
   remove_copy(coll1.begin(), coll1.end(),       // source
               ostream_iterator<int>(cout," "),  // destination
               3);                               // removed value
   cout << endl;

}</source>

1 2 3 4 5 6 1 2 3 4 5 6 7 8 9
1 2 4 5 6 1 2 4 5 6 7 8 9

Use remove_copy with vector

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

1. include <vector>
2. include <algorithm>

using namespace std;

int main() {

 char str[] = "This is a test.";
 vector<char> v, v2(30);
 unsigned int i;
  
 for(i=0; str[i]; i++) v.push_back(str[i]);
  
 for(i=0; i<v.size(); i++) {
    cout << v[i] << endl;
 }
 
 remove_copy(v.begin(), v.end(), v2.begin(), " ");
  
 for(i=0; i<v2.size(); i++) cout << v2[i];
 cout << endl << endl;
 
 return 0;

}</source>