The sample code below illustrates how to use the predicate version of the partial_sort_copy
STL function in Visual C++.
Required Header:
<algorithm>
template<class InputIterator, RandomAccessIterator, class Compare> inline
RandomAccessIterator partial_sort(InputIterator first1,
InputIterator last1,
RandomAccessIterator first2,
RandomAccessIterator last2,
Compare compare)
Note: The class/parameter names in the prototype do not match the version in the header file. Some have been modified to improve readability.
Description:
The partial_sort_copy algorithm sorts the smallest N elements, where N = min((last1 - first1), (last2 - first2)), of the sequence [first1, last1), and copies the results to the sequence [first2, first2 + N]. The predicate version of partial_sort_copy uses the compare function for comparisons.
Sample Code:
//////////////////////////////////////////////////////////////////////
//
// Compile options needed: /GX
//
// partial_sort_copyP.cpp : Illustrates how to use the predicate version
// of the partial_sort_copy function.
//
// Functions:
//
// partial_sort_copy : Sort the smallest N elements in a sequence
// and copy the resulting sequence
// to another sequence.
//////////////////////////////////////////////////////////////////////
// disable warning C4786: symbol greater than 255 character,
// okay to ignore
#pragma warning(disable: 4786)
#include <iostream>
#include <algorithm>
#include <functional>
#include <vector>
using namespace std ;
void main()
{
const int VECTOR_SIZE = 8 ;
// Define a template class vector of int
typedef vector<int> IntVector ;
//Define an iterator for template class vector of strings
typedef IntVector::iterator IntVectorIt ;
IntVector Numbers(VECTOR_SIZE) ;
IntVector Result(4) ;
IntVectorIt start, end, it ;
// Initialize vector Numbers
Numbers[0] = 4 ;
Numbers[1] = 10;
Numbers[2] = 70 ;
Numbers[3] = 30 ;
Numbers[4] = 10;
Numbers[5] = 69 ;
Numbers[6] = 96 ;
Numbers[7] = 7;
start = Numbers.begin() ; // location of first
// element of Numbers
end = Numbers.end() ; // one past the location
// last element of Numbers
cout << "Before calling partial_sort_copy\n" << endl ;
// print content of Numbers
cout << "Numbers { " ;
for(it = start; it != end; it++)
cout << *it << " " ;
cout << " }\n" << endl ;
// sort the smallest 4 elements in the Numbers
// and copy the results in Result
partial_sort_copy(start, end, Result.begin(),Result.end(),less<int>());
cout << "After calling partial_sort_copy\n" << endl ;
cout << "Numbers { " ;
for(it = start; it != end; it++)
cout << *it << " " ;
cout << " }\n" << endl ;
cout << "Result { " ;
for(it = Result.begin(); it != Result.end(); it++)
cout << *it << " " ;
cout << " }\n" << endl ;
}
Program Output is:
Before calling partial_sort_copy
Numbers { 4 10 70 30 10 69 96 7 }
After calling partial_sort_copy
Numbers { 4 10 70 30 10 69 96 7 }
Result { 4 7 10 10 }