std::sort_heap() algorithm
- since C++20
- until C++20
template< class RandomIt >
constexpr void sort_heap( RandomIt first, RandomIt last );
// (2)
template< class RandomIt, class Compare >
constexpr void sort_heap( RandomIt first, RandomIt last, Compare comp );
template< class RandomIt >
void sort_heap( RandomIt first, RandomIt last );
// (2)
template< class RandomIt, class Compare >
void sort_heap( RandomIt first, RandomIt last, Compare comp );
Converts the max heap [first
; last
) into a sorted range in ascending order.
The resulting range no longer has the heap property.
-
(1) Elements are compared using
operator<
. -
(2) Elements are compared using the given binary comparison function
comp
.
Parameters
first last | The range of elements to sort. |
policy | The execution policy to use. See execution policy for details. |
comp | Comparison function object (i.e. an object that satisfies the requirements of Compare). The signature of the comparison function should be equivalent to the following:
|
Type requirements
RandomIt | LegacyRandomAccessIterator LegacyRandomAccessIterator |
The type defereferenced RandomIt | MoveAssignable MoveConstructible |
Return value
(none)
Complexity
Given N
as std::distance(first, last)
:
At most 2 * N * log(N) comparisons.
Exceptions
The overloads with a template parameter named ExecutionPolicy
report errors as follows:
- If execution of a function invoked as part of the algorithm throws an exception and
ExecutionPolicy
is one of the standard policies,std::terminate
is called. For any otherExecutionPolicy
, the behavior is implementation-defined. - If the algorithm fails to allocate memory,
std::bad_alloc
is thrown.
Possible implementation
sort_heap(1)
template<class RandomIt>
void sort_heap(RandomIt first, RandomIt last)
{
while (first != last)
std::pop_heap(first, last--);
}
sort_heap(2)
template<class RandomIt, class Compare>
void sort_heap(RandomIt first, RandomIt last, Compare comp)
{
while (first != last)
std::pop_heap(first, last--, comp);
}
Notes
A max heap is a range of elements [f
; l
) that has the following properties:
- Given
N
asl - f
, for all0 < i < N
,f[(i - 1) / 2]
does not compare less thanf[i]
. - A new element can be added using
std::push_heap
, in O(log(N)) time. - The first element can be removed using
std::pop_heap
, in O(log(N)) time.
Examples
#include <algorithm>
#include <iostream>
#include <string_view>
#include <vector>
void println(std::string_view fmt, auto const& v)
{
for (std::cout << fmt; const auto &i : v)
std::cout << i << ' ';
std::cout << '\n';
}
int main()
{
std::vector<int> v {3, 1, 4, 1, 5, 9};
std::sort_heap(v.begin(), v.end());
println("after sort_heap, v: ", v);
std::sort_heap(v.begin(), v.end());
println("after sort_heap, v: ", v);
}
after sort_heap, v: 9 4 5 1 1 3
after sort_heap, v: 1 1 3 4 5 9
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