std::priority_queue< _Tp, _Sequence, _Compare >

Section: C Library Functions (3)
Updated: Wed Apr 17 2019
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NAME

std::priority_queue< _Tp, _Sequence, _Compare > - A standard container automatically sorting its contents.

SYNOPSIS

Public Types

typedef _Sequence::const_reference const_reference

typedef _Sequence container_type

typedef _Sequence::reference reference

typedef _Sequence::size_type size_type

typedef _Compare value_compare

typedef _Sequence::value_type value_type

Public Member Functions

template<typename _Seq = _Sequence, typename _Requires = typename enable_if<__and_<is_default_constructible<_Compare>,is_default_constructible<_Seq>>::value>::type> priority_queue ()
Default constructor creates no elements.
priority_queue (const _Compare &__x, const _Sequence &__s)

priority_queue (const _Compare &__x, _Sequence &&__s=_Sequence())

template<typename _Alloc , typename _Requires = _Uses<_Alloc>> priority_queue (const _Alloc &__a)

template<typename _Alloc , typename _Requires = _Uses<_Alloc>> priority_queue (const _Compare &__x, const _Alloc &__a)

template<typename _Alloc , typename _Requires = _Uses<_Alloc>> priority_queue (const _Compare &__x, const _Sequence &__c, const _Alloc &__a)

template<typename _Alloc , typename _Requires = _Uses<_Alloc>> priority_queue (const _Compare &__x, _Sequence &&__c, const _Alloc &__a)

template<typename _Alloc , typename _Requires = _Uses<_Alloc>> priority_queue (const priority_queue &__q, const _Alloc &__a)

template<typename _Alloc , typename _Requires = _Uses<_Alloc>> priority_queue (priority_queue &&__q, const _Alloc &__a)

template<typename _InputIterator > priority_queue (_InputIterator __first, _InputIterator __last, const _Compare &__x, const _Sequence &__s)
Builds a queue from a range.
template<typename _InputIterator > priority_queue (_InputIterator __first, _InputIterator __last, const _Compare &__x=_Compare(), _Sequence &&__s=_Sequence())

template<typename... _Args> void emplace (_Args &&... __args)

bool empty () const

void pop ()
Removes first element.
void push (const value_type &__x)
Add data to the queue.
void push (value_type &&__x)

size_type size () const

void swap (priority_queue &__pq) noexcept(__and_<//c++1z or gnu++11 __is_nothrow_swappable< _Sequence >, __is_nothrow_swappable< _Compare > >::value)

const_reference top () const

Protected Attributes

_Sequence c

_Compare comp

Detailed Description

template<typename _Tp, typename _Sequence = vector<_Tp>, typename _Compare = less<typename _Sequence::value_type>>

class std::priority_queue< _Tp, _Sequence, _Compare >" A standard container automatically sorting its contents.

Template Parameters:

: _Tp Type of element.
_Sequence Type of underlying sequence, defaults to vector<_Tp>.
_Compare Comparison function object type, defaults to less<_Sequence::value_type>.

This is not a true container, but an adaptor. It holds another container, and provides a wrapper interface to that container. The wrapper is what enforces priority-based sorting and queue behavior. Very few of the standard container/sequence interface requirements are met (e.g., iterators).

The second template parameter defines the type of the underlying sequence/container. It defaults to std::vector, but it can be any type that supports front(), push_back, pop_back, and random-access iterators, such as std::deque or an appropriate user-defined type.

The third template parameter supplies the means of making priority comparisons. It defaults to less<value_type> but can be anything defining a strict weak ordering.

Members not found in normal containers are container_type, which is a typedef for the second Sequence parameter, and push, pop, and top, which are standard queue operations.

Note:

: No equality/comparison operators are provided for priority_queue.
Sorting of the elements takes place as they are added to, and removed from, the priority_queue using the priority_queue's member functions. If you access the elements by other means, and change their data such that the sorting order would be different, the priority_queue will not re-sort the elements for you. (How could it know to do so?)

Definition at line 435 of file stl_queue.h.

Constructor & Destructor Documentation

template<typename _Tp, typename _Sequence = vector<_Tp>, typename _Compare = less<typename _Sequence::value_type>> template<typename _Seq = _Sequence, typename _Requires = typename enable_if<__and_<is_default_constructible<_Compare>,is_default_constructible<_Seq>>::value>::type> std::priority_queue< _Tp, _Sequence, _Compare >::priority_queue () [inline]

Default constructor creates no elements.

Definition at line 485 of file stl_queue.h.

template<typename _Tp, typename _Sequence = vector<_Tp>, typename _Compare = less<typename _Sequence::value_type>> template<typename _InputIterator > std::priority_queue< _Tp, _Sequence, _Compare >::priority_queue (_InputIterator __first, _InputIterator __last, const _Compare & __x, const _Sequence & __s) [inline]

Builds a queue from a range.

Parameters:

: __first An input iterator.
__last An input iterator.
__x A comparison functor describing a strict weak ordering.
__s An initial sequence with which to start.

Begins by copying __s, inserting a copy of the elements from [first,last) into the copy of __s, then ordering the copy according to __x.

For more information on function objects, see the documentation on functor base classes.

Definition at line 553 of file stl_queue.h.

Member Function Documentation

template<typename _Tp, typename _Sequence = vector<_Tp>, typename _Compare = less<typename _Sequence::value_type>> bool std::priority_queue< _Tp, _Sequence, _Compare >::empty () const [inline]

Returns true if the queue is empty.

Definition at line 579 of file stl_queue.h.

template<typename _Tp, typename _Sequence = vector<_Tp>, typename _Compare = less<typename _Sequence::value_type>> void std::priority_queue< _Tp, _Sequence, _Compare >::pop () [inline]

Removes first element. This is a typical queue operation. It shrinks the queue by one. The time complexity of the operation depends on the underlying sequence.

Note that no data is returned, and if the first element's data is needed, it should be retrieved before pop() is called.

Definition at line 642 of file stl_queue.h.

template<typename _Tp, typename _Sequence = vector<_Tp>, typename _Compare = less<typename _Sequence::value_type>> void std::priority_queue< _Tp, _Sequence, _Compare >::push (const value_type & __x) [inline]

Add data to the queue.

Parameters:

: __x Data to be added.

This is a typical queue operation. The time complexity of the operation depends on the underlying sequence.

Definition at line 607 of file stl_queue.h.

References std::push_heap().

template<typename _Tp, typename _Sequence = vector<_Tp>, typename _Compare = less<typename _Sequence::value_type>> size_type std::priority_queue< _Tp, _Sequence, _Compare >::size () const [inline]

Returns the number of elements in the queue.

Definition at line 584 of file stl_queue.h.

template<typename _Tp, typename _Sequence = vector<_Tp>, typename _Compare = less<typename _Sequence::value_type>> const_reference std::priority_queue< _Tp, _Sequence, _Compare >::top () const [inline]

Returns a read-only (constant) reference to the data at the first element of the queue.

Definition at line 592 of file stl_queue.h.

Author

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