C++ Tutorial/STL Algorithms Sorting/partial sort copy

Use partial_sort_copy to copy elements in one container sorted into another container

<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() {

   deque<int> coll1;
   vector<int> coll6(6);      // initialize with 6 elements
   vector<int> coll30(30);    // initialize with 30 elements
   INSERT_ELEMENTS(coll1,3,7);
   INSERT_ELEMENTS(coll1,2,6);
   INSERT_ELEMENTS(coll1,1,5);
   PRINT_ELEMENTS(coll1);
   // copy elements of coll1 sorted into coll6
   vector<int>::iterator pos6;
   pos6 = partial_sort_copy (coll1.begin(), coll1.end(),
                             coll6.begin(), coll6.end());
   // print all copied elements
   copy (coll6.begin(), pos6,ostream_iterator<int>(cout," "));
   cout << endl;

}</source>

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Use partial_sort_copy with custom comparison function to copy elements in one container sorted into another container

<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() {

   deque<int> coll1;
   vector<int> coll6(6);      // initialize with 6 elements
   vector<int> coll30(30);    // initialize with 30 elements
   INSERT_ELEMENTS(coll1,3,7);
   INSERT_ELEMENTS(coll1,2,6);
   INSERT_ELEMENTS(coll1,1,5);
   PRINT_ELEMENTS(coll1);
   // copy elements of coll1 sorted into coll30
   vector<int>::iterator pos30;
   pos30 = partial_sort_copy (coll1.begin(), coll1.end(),
                              coll30.begin(), coll30.end(),
                              greater<int>());
   // print all copied elements
   copy (coll30.begin(), pos30,
         ostream_iterator<int>(cout," "));
   cout << endl;

}</source>

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