C++/STL Algorithms Modifying sequence operations/copy backward

Use std::copy_backward to place elements in one vector into another vector in reverse order

<source lang="cpp">

1. include <iostream>

using std::cout; using std::endl;

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

int main() {

  int a1[ 5 ] = { 1, 3, 5, 7, 9 };
  int a2[ 5 ] = { 2, 4, 5, 7, 9 };
  
  std::vector< int > v1( a1, a1 + 5 );
  std::vector< int > v2( a2, a2 + 5 );
  
  std::ostream_iterator< int > output( cout, " " );
  std::copy( v1.begin(), v1.end(), output ); // display vector output
  std::copy( v2.begin(), v2.end(), output ); // display vector output
  std::vector< int > results( v1.size() );
  // place elements of v1 into results in reverse order
  std::copy_backward( v1.begin(), v1.end(), results.end() );
  cout << "\n\nAfter copy_backward, results contains: ";
  std::copy( results.begin(), results.end(), output );
  
  cout << endl;
  return 0;

}

/* 1 3 5 7 9 2 4 5 7 9 After copy_backward, results contains: 1 3 5 7 9

• /

 </source>

Use the copy_backward algorithms: Shift it right by 2 positions

<source lang="cpp">

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

using namespace std; int main() {

 string s("abcdefghihklmnopqrstuvwxyz");
 vector<char> vector1(s.begin(), s.end());
 copy_backward(vector1.begin(), vector1.end() - 2, vector1.end());
 vector<char>::iterator pos;
 for (pos=vector1.begin(); pos!=vector1.end(); ++pos) {
       cout << *pos << " ";
 }
 return 0;

} /* a b a b c d e f g h i h k l m n o p q r s t u v w x

*/
 </source>