C++ Tutorial/STL Algorithms Non modifying sequence operations/copy backward

copy_backward, merge, unique and reverse.

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

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

using namespace std; int main() {

  const int SIZE = 5;
  int a1[ SIZE ] = { 1, 3, 5, 7, 9 };
  int a2[ SIZE ] = { 2, 4, 5, 7, 9 };
  vector< int > v1( a1, a1 + SIZE );
  vector< int > v2( a2, a2 + SIZE );
  vector< int > results( v1.size() );
  copy_backward( v1.begin(), v1.end(), results.end() );
  
  vector< int > results2( v1.size() + v2.size() );
  merge( v1.begin(), v1.end(), v2.begin(), v2.end(),results2.begin() );
  
  vector< int >::iterator endLocation;
  endLocation = unique( results2.begin(), results2.end() );
  reverse( v1.begin(), v1.end() );
  cout << endl;
  return 0;

}</source>

Use copy_backward to copy value from vector to a list

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

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

using namespace std; int main (){

   list <int> l;
   for (int nCount = 0; nCount < 10; ++ nCount)
       l.push_back (nCount);
   list <int>::const_iterator li;
   for ( li = l.begin (); li != l.end (); ++ li )
       cout << *li << " ";
   vector <int> v (l.size () * 2);
   copy_backward ( l.begin (), l.end (), v.end () );
   vector <int>::const_iterator vi;
   for ( vi = v.begin (); vi != v.end (); ++ vi )
       cout << *vi << " ";
   return 0;

}</source>

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

<source lang="cpp">#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;

}</source>

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

Use the copy_backward algorithms: Shift it right by 2 positions

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

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

}</source>

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