std::is_heap_until() algorithm
- od C++20
- od C++17
- od C++11
// (1)
template< class RandomIt >
constexpr RandomIt is_heap_until( RandomIt first, RandomIt last );
// (2)
template< class RandomIt, class Compare >
constexpr RandomIt is_heap_until( RandomIt first, RandomIt last, Compare comp );
// (3)
template< class ExecutionPolicy, class RandomIt >
RandomIt is_heap_until( ExecutionPolicy&& policy, RandomIt first, RandomIt last );
// (4)
template< class ExecutionPolicy, class RandomIt, class Compare >
RandomIt is_heap_until( ExecutionPolicy&& policy, RandomIt first, RandomIt last, Compare comp );
// (1)
template< class RandomIt >
RandomIt is_heap_until( RandomIt first, RandomIt last );
// (2)
template< class RandomIt, class Compare >
RandomIt is_heap_until( RandomIt first, RandomIt last, Compare comp );
// (3)
template< class ExecutionPolicy, class RandomIt >
RandomIt is_heap_until( ExecutionPolicy&& policy, RandomIt first, RandomIt last );
// (4)
template< class ExecutionPolicy, class RandomIt, class Compare >
RandomIt is_heap_until( ExecutionPolicy&& policy, RandomIt first, RandomIt last, Compare comp );
// (1)
template< class RandomIt >
RandomIt is_heap_until( RandomIt first, RandomIt last );
// (2)
template< class RandomIt, class Compare >
RandomIt is_heap_until( RandomIt first, RandomIt last, Compare comp );
Examines the range [first
; last
) and finds the largest range beginning at first
which is a max heap.
-
(1) Elements are compared using
operator<
. -
(2) Elements are compared using the given binary comparison function
comp
. -
(3 - 4) Same as (1 - 2), but executed according to
policy
.Overload ResolutionThese overloads participate in overload resolution only if
std::is_execution_policy_v<std::decay_t<ExecutionPolicy>>
(do C++20)std::is_execution_policy_v<std::remove_cvref_t<ExecutionPolicy>>
(od C++20) istrue
.
Parameters
first last | The range of elements to examine. |
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 |
Return value
The upper bound of the largest range beginning at first
which is a max heap.
That is, the last iterator it for which range [first
; it
) is a max heap.
Complexity
Linear in the distance between first
and last
.
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.
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 <vector>
int main()
{
std::vector<int> v {3, 1, 4, 1, 5, 9};
std::make_heap(v.begin(), v.end());
// probably mess up the heap
v.push_back(2);
v.push_back(6);
auto heap_end = std::is_heap_until(v.begin(), v.end());
std::cout << "all of v: ";
for (auto i : v) std::cout << i << ' ';
std::cout << '\n';
std::cout << "only heap: ";
for (auto i = v.begin(); i != heap_end; ++i) std::cout << *i << ' ';
std::cout << '\n';
}
all of v: 9 5 4 1 1 3 2 6
only heap: 9 5 4 1 1 3 2
Hover to see the original license.