< cpp‎ | algorithm
Revision as of 05:53, 17 June 2013 by Cubbi (Talk | contribs)

Algorithm library
Execution policies (C++17)
Non-modifying sequence operations
Modifying sequence operations
Operations on uninitialized storage
Partitioning operations
Sorting operations
Binary search operations
Set operations (on sorted ranges)
Heap operations
Minimum/maximum operations

Numeric operations
C library
Defined in header <algorithm>
template< class RandomIt >
void partial_sort( RandomIt first, RandomIt middle, RandomIt last );
template< class RandomIt, class Compare >
void partial_sort( RandomIt first, RandomIt middle, RandomIt last, Compare comp );

Sorts some of the elements in the range [first, last) in ascending order. The first middle - first of these elements are placed in the range [first, middle). 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.



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 the second.

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

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

The signature does not need to have const &, but the function object must not modify the objects passed to it.
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
RandomIt must meet the requirements of ValueSwappable and RandomAccessIterator.
The type of dereferenced RandomIt must meet the requirements of MoveAssignable and MoveConstructible.

Return value



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


#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 << " ";


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]