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==The generic partial_sort algorithms with predicate==

<source lang="cpp">

#include <vector>
#include <algorithm>
#include <iostream>
#include <iterator>
using namespace std;
class comp_last {
public:
bool operator()(int x, int y) const
// Compare x and y based on their last base-10 digits:
{
return x 10;
}
};
int main()
{
const int N = 20;
vector<int> vector0;
for (int i = 0; i < N; ++i)
vector0.push_back(i);
vector<int> vector1 = vector0;
ostream_iterator<int> out(cout, " ");
cout << "Before sorting:\n";
copy(vector1.begin(), vector1.end(), out);
cout << endl;
sort(vector1.begin(), vector1.end(), comp_last());

cout << "After sorting by last digits with sort:\n";
copy(vector1.begin(), vector1.end(), out);
cout << endl << endl;
vector1 = vector0;
reverse(vector1.begin(), vector1.end());
cout << "Before sorting:\n";
copy(vector1.begin(), vector1.end(), out);
cout << endl << endl;
partial_sort(vector1.begin(), vector1.begin() + 5,vector1.end(), comp_last());
cout << "After sorting with partial_sort to get 5 values with smallest last d
igits:\n";
copy(vector1.begin(), vector1.end(), out);
cout << endl << endl;
return 0;
}
/*
Before sorting:
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
After sorting by last digits with sort:
10 0 11 1 12 2 13 3 4 14 5 15 6 16 7 17 8 18 9 19
Before sorting:
19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
After sorting with partial_sort to get 5 values with smallest last digits:
10 0 11 1 12 19 18 17 16 15 9 8 7 6 5 4 14 13 3 2

*/
</source>

==Use partial_sort to sort all 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.
*/
#include <iostream>
#include <vector>
#include <deque>
#include <list>
#include <set>
#include <map>
#include <string>
#include <algorithm>
#include <iterator>
#include <functional>
#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> coll;
INSERT_ELEMENTS(coll,3,7);
INSERT_ELEMENTS(coll,2,6);
INSERT_ELEMENTS(coll,1,5);
PRINT_ELEMENTS(coll);
// sort all elements
partial_sort (coll.begin(), // beginning of the range
coll.end(), // end of sorted range
coll.end()); // end of full range
PRINT_ELEMENTS(coll);
}
/*
3 4 5 6 7 2 3 4 5 6 1 2 3 4 5
1 2 2 3 3 3 4 4 4 5 5 5 6 6 7
*/

</source>

==Use partial_sort to sort until the first five elements are sorted==

<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.
*/
#include <iostream>
#include <vector>
#include <deque>
#include <list>
#include <set>
#include <map>
#include <string>
#include <algorithm>
#include <iterator>
#include <functional>
#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> coll;
INSERT_ELEMENTS(coll,3,7);
INSERT_ELEMENTS(coll,2,6);
INSERT_ELEMENTS(coll,1,5);
PRINT_ELEMENTS(coll);
// sort until the first five elements are sorted
partial_sort (coll.begin(), // beginning of the range
coll.begin()+5, // end of sorted range
coll.end()); // end of full range
PRINT_ELEMENTS(coll);
}
/*
3 4 5 6 7 2 3 4 5 6 1 2 3 4 5
1 2 2 3 3 7 6 5 5 6 4 4 3 4 5
*/

</source>

==Use partial_sort with custom function to sort inversely until the first five elements are sorted==

<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.
*/
#include <iostream>
#include <vector>
#include <deque>
#include <list>
#include <set>
#include <map>
#include <string>
#include <algorithm>
#include <iterator>
#include <functional>
#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> coll;
INSERT_ELEMENTS(coll,3,7);
INSERT_ELEMENTS(coll,2,6);
INSERT_ELEMENTS(coll,1,5);
PRINT_ELEMENTS(coll);
// sort inversely until the first five elements are sorted
partial_sort (coll.begin(), // beginning of the range
coll.begin()+5, // end of sorted range
coll.end(), // end of full range
greater<int>()); // sorting criterion
PRINT_ELEMENTS(coll);
}
/*
3 4 5 6 7 2 3 4 5 6 1 2 3 4 5
7 6 6 5 5 2 3 3 4 4 1 2 3 4 5
*/
</source>

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