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# Predicate Version of partial_sort

Visual Studio 2005

Illustrates how to use the predicate version of the partial_sort Standard Template Library (STL) function in Visual C++.

```
template<class RandomAccessIterator, class Compare> inline
void partial_sort(
RandomAccessIterator First,
RandomAccessIterator Middle,
RandomAccessIterator Last,
Compare Compare
)
```

## Remarks

Note

The class/parameter names in the prototype do not match the version in the header file. Some have been modified to improve readability.

The partial_sort algorithm sorts the smallest n elements, where n = Middle - First of the sequence [First, Last). The remaining elements end up in the range [Middle..Last) in an undefined order. The predicate version of partial_sort uses the compare function for comparisons.

## Example

```// partial_sortPV.cpp
// compile with: /EHsc
// Illustrates how to use the predicate version
// of the partial_sort function.
//
// Functions:
//    partial_sort : Sort the smallest N elements in a 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 ;

int 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) ;

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\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 sequence
partial_sort(start, start+4, end, less<int>()) ;

cout << "After calling partial_sort\n" << endl ;

cout << "Numbers { " ;
for(it = start; it != end; it++)
cout << *it << " " ;
cout << " }\n" << endl ;
}
```

## Output

```Before calling partial_sort

Numbers { 4 10 70 30 10 69 96 7  }

After calling partial_sort

Numbers { 4 7 10 10 70 69 96 30  }```