C++ Tutorial/STL Algorithms Modifying sequence operations/reverse

Reverse a stack of integers

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

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

using namespace std;

int main() {

 vector<int> v;
 unsigned int i;
  
 for(i=0; i<10; i++) v.push_back(i);
  
 cout << "Initial: ";
 for(i=0; i<v.size(); i++) 
    cout << v[i] << endl;
  
 reverse(v.begin(), v.end());
  
 for(i=0; i<v.size(); i++) 
   cout << v[i] << endl;
  
 return 0;

}</source>

Reverse the order of the found element with value 3 and all following elements

<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 <algorithm>

using namespace std; int main() {

   vector<int> coll;
   vector<int>::iterator pos;
   // insert elements from 1 to 6 in arbitrary order
   coll.push_back(2);
   coll.push_back(5);
   coll.push_back(4);
   coll.push_back(1);
   coll.push_back(6);
   coll.push_back(3);
   // find the first element with value 3
   pos = find (coll.begin(), coll.end(),  // range
               3);                        // value
   // reverse the order of the found element with value 3 and all following elements
   reverse (pos, coll.end());
   // print all elements
   for (pos=coll.begin(); pos!=coll.end(); ++pos) {
       cout << *pos << " ";
   }
   cout << endl;

}</source>

2 5 4 1 6 3

Use reverse to reverse order from second to last element but one

<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() {

   vector<int> coll;
   INSERT_ELEMENTS(coll,1,9);
   PRINT_ELEMENTS(coll,"coll: ");
   // reverse order from second to last element but one
   reverse (coll.begin()+1, coll.end()-1);
   PRINT_ELEMENTS(coll,"coll: ");

}</source>

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

Use reverse to reverse the order of elements

<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() {

   vector<int> coll;
   INSERT_ELEMENTS(coll,1,9);
   PRINT_ELEMENTS(coll,"coll: ");
   // reverse order of elements
   reverse (coll.begin(), coll.end());
   PRINT_ELEMENTS(coll,"coll: ");

}</source>

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

Using the STL generic reverse algorithm with a vector

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

1. include <vector>
2. include <cassert>
3. include <algorithm> // For reverse

using namespace std; template <typename Container> Container make(const char s[]) {

 return Container(&s[0], &s[strlen(s)]);

} int main() {

 vector<char> vector1 = make< vector<char> >("abc");
 reverse(vector1.begin(), vector1.end());
 assert (vector1 == make< vector<char> >("cba"));
 return 0;

}</source>