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# Predicate Version of partial_sort_copy

Visual Studio 2005

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

```
template<class InputIterator, RandomAccessIterator, class Compare> inline
RandomAccessIterator partial_sort(
InputIterator First1,
InputIterator Last1,
RandomAccessIterator First2,
RandomAccessIterator Last2,
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_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.

## Example

```// partial_sort_copyP.cpp
// compile with: /EHsc
// 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 ;

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);
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());

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;
}
```

## Output

```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  }```

## Requirements

#### Concepts

Standard Template Library Samples

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