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Difference between revisions of "cpp/algorithm/partial sort"

From cppreference.com
< cpp‎ | algorithm
(cmp ord)
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  | output=
 
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0 1 2 7 8 6 5 9 4 3
 
0 1 2 7 8 6 5 9 4 3
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| p=true
 
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Revision as of 08:02, 16 May 2015

 
 
Algorithm library
Constrained algorithms and algorithms on ranges (C++20)
Constrained algorithms, e.g. ranges::copy, ranges::sort, ...
Execution policies (C++17)
Non-modifying sequence operations
Batch operations
(C++17)
Search operations
(C++11)                (C++11)(C++11)

Modifying sequence operations
Copy operations
(C++11)
(C++11)
Swap operations
Transformation operations
Generation operations
Removing operations
Order-changing operations
(until C++17)(C++11)
(C++20)(C++20)
Sampling operations
(C++17)

Sorting and related operations
Partitioning operations
Sorting operations
Binary search operations
(on partitioned ranges)
Set operations (on sorted ranges)
Merge operations (on sorted ranges)
Heap operations
Minimum/maximum operations
(C++11)
(C++17)
Lexicographical comparison operations
Permutation operations
C library
Numeric operations
Operations on uninitialized memory
 
Defined in header <algorithm>
template< class RandomIt >
void partial_sort( RandomIt first, RandomIt middle, RandomIt last );
(1)
template< class RandomIt, class Compare >
void partial_sort( RandomIt first, RandomIt middle, RandomIt last, Compare comp );
(2)

Rearranges elements such that the range [first, middle) contains the sorted middle - first smallest elements in the range [first, last).

The order of equal elements is not guaranteed to be preserved. The order of the remaining elements in the range [middle, last) is unspecified. The first version uses operator< to compare the elements, the second version uses the given comparison function comp.

Contents

Parameters

first, last - the range of elements to sort
comp - comparison function object (i.e. an object that satisfies the requirements of Compare) which returns ​true if the first argument is less than (i.e. is ordered before) the second.

The signature of the comparison function should be equivalent to the following:

bool cmp(const Type1& a, const Type2& b);

While the signature does not need to have const&, the function must not modify the objects passed to it and must be able to accept all values of type (possibly const) Type1 and Type2 regardless of value category (thus, Type1& is not allowed, nor is Type1 unless for Type1 a move is equivalent to a copy(since C++11)).
The types Type1 and Type2 must be such that an object of type RandomIt can be dereferenced and then implicitly converted to both of them. ​

Type requirements

Template:par req concept Template:par req concept deref

Return value

(none)

Complexity

Approximately (last-first)log(middle-first)) applications of cmp

Example

#include <algorithm>
#include <functional>
#include <array>
#include <iostream>
 
int main()
{
    std::array<int, 10> s{5, 7, 4, 2, 8, 6, 1, 9, 0, 3};
 
    std::partial_sort(s.begin(), s.begin() + 3, s.end());
    for (int a : s) {
        std::cout << a << " ";
    } 
}

Possible output:

0 1 2 7 8 6 5 9 4 3

See also

partially sorts the given range making sure that it is partitioned by the given element
(function template) [edit]
copies and partially sorts a range of elements
(function template) [edit]
sorts a range of elements while preserving order between equal elements
(function template) [edit]
sorts a range into ascending order
(function template) [edit]