Standard C++ Library
Copyright 1998, Rogue Wave Software, Inc.
NAME
partial_sort_copy
- Templatized algorithm for sorting collections of enti-
ties.
SYNOPSIS
#include <algorithm>
template <class InputIterator,
class RandomAccessIterator>
void partial_sort_copy (InputIterator first,
InputIterator last,
RandomAccessIterator result_first,
RandomAccessIterator result_last);
template <class InputIterator,
class RandomAccessIterator,
class Compare>
void partial_sort_copy (InputIterator first,
InputIterator last,
RandomAccessIterator result_first,
RandomAccessIterator result_last,
Compare comp);
DESCRIPTION
The partial_sort_copy algorithm places the smaller of last -
first and result_last - result_first sorted elements from
the range [first, last) into the range beginning at
result_first (in other words, the range: [result_first,
result_first+min(last - first, result_last - result_first)).
The effect is as if the range [first,last) were placed in a
temporary buffer, sorted, and then as many elements as pos-
sible copied into the range [result_first, result_last).
The first version of the algorithm uses less than (opera-
tor<) as the comparison operator for the sort. The second
version uses the comparison function comp.
COMPLEXITY
partial_sort_copy does approximately (last-first) *
log(min(last-first, result_last-result_first)) comparisons.
EXAMPLE
//
// partsort.cpp
#include <vector>
#include <algorithm>
#include <iostream>
using namespace std;
int main()
{
int d1[20] = {17, 3, 5, -4, 1, 12, -10, -1, 14, 7,
-6, 8, 15, -11, 2, -2, 18, 4, -3, 0};
//
// Set up a vector.
//
vector<int> v1(d1+0, d1+20);
//
// Output original vector.
//
cout << "For the vector: ";
copy(v1.begin(), v1.end(),
ostream_iterator<int>(cout," "));
//
// Partial sort the first seven elements.
//
partial_sort(v1.begin(), v1.begin()+7, v1.end());
//
// Output result.
//
cout << endl << endl << "A partial_sort of 7
elements gives: "
<< endl << " ";
copy(v1.begin(), v1.end(),
ostream_iterator<int,char>(cout," "));
cout << endl;
//
// A vector of ten elements.
vector<int> v2(10, 0);
//
// Sort the last ten elements in v1 into v2.
partial_sort_copy(v1.begin()+10, v1.end(),
v2.begin(),<br> v2.end());
//
// Output result.
cout << endl << "A partial_sort_copy of the last
ten elements gives: " << endl << " ";
copy(v2.begin(), v2.end(),
ostream_iterator<int,char>(cout," "));
cout << endl;
return 0;
}
Program Output
For the vector: 17 3 5 -4 1 12 -10 -1 14 7 -6 8 15 -11 2 -2
18 4 -3 0
A partial_sort of seven elements gives:
-11 -10 -6 -4 -3 -2 -1 17 14 12 7 8 15 5 3 2 18 4 1 0
A partial_sort_copy of the last ten elements gives:
0 1 2 3 4 5 7 8 15 18
WARNINGS
If your compiler does not support default template parame-
ters, then you need to always include the Allocator template
argument. For instance, you need to write:
vector<int, allocator<int> >
instead of:
vector<int>
If your compiler does not support namespaces, then you do
not need the using declaration for std.
SEE ALSO
sort, stable_sort, partial_sort