Any sequence container with random access iterator and supporting operations front(), push_back() and pop_back() can be used to instantiate priority_queue. In particular, vector ([vector]) and deque ([deque]) can be used. Instantiating priority_queue also involves supplying a function or function object for making priority comparisons; the library assumes that the function or function object defines a strict weak ordering ([alg.sorting]).
namespace std {
template <class T, class Container = vector<T>,
class Compare = default_order_t<typename Container::value_type>>
class priority_queue {
public:
using value_type = typename Container::value_type;
using reference = typename Container::reference;
using const_reference = typename Container::const_reference;
using size_type = typename Container::size_type;
using container_type = Container;
using value_compare = Compare;
protected:
Container c;
Compare comp;
public:
priority_queue(const Compare& x, const Container&);
explicit priority_queue(const Compare& x = Compare(), Container&& = Container());
template <class InputIterator>
priority_queue(InputIterator first, InputIterator last,
const Compare& x, const Container&);
template <class InputIterator>
priority_queue(InputIterator first, InputIterator last,
const Compare& x = Compare(), Container&& = Container());
template <class Alloc> explicit priority_queue(const Alloc&);
template <class Alloc> priority_queue(const Compare&, const Alloc&);
template <class Alloc> priority_queue(const Compare&, const Container&, const Alloc&);
template <class Alloc> priority_queue(const Compare&, Container&&, const Alloc&);
template <class Alloc> priority_queue(const priority_queue&, const Alloc&);
template <class Alloc> priority_queue(priority_queue&&, const Alloc&);
bool empty() const { return c.empty(); }
size_type size() const { return c.size(); }
const_reference top() const { return c.front(); }
void push(const value_type& x);
void push(value_type&& x);
template <class... Args> void emplace(Args&&... args);
void pop();
void swap(priority_queue& q) noexcept(is_nothrow_swappable_v<Container> &&
is_nothrow_swappable_v<Compare>)
{ using std::swap; swap(c, q.c); swap(comp, q.comp); }
};
// no equality is provided
template <class T, class Container, class Compare>
void swap(priority_queue<T, Container, Compare>& x,
priority_queue<T, Container, Compare>& y) noexcept(noexcept(x.swap(y)));
template <class T, class Container, class Compare, class Alloc>
struct uses_allocator<priority_queue<T, Container, Compare>, Alloc>
: uses_allocator<Container, Alloc>::type { };
}
priority_queue(const Compare& x, const Container& y);
explicit priority_queue(const Compare& x = Compare(), Container&& y = Container());
Requires: x shall define a strict weak ordering ([alg.sorting]).
Effects: Initializes comp with x and c with y (copy constructing or move constructing as appropriate); calls make_heap(c.begin(), c.end(), comp).
template <class InputIterator>
priority_queue(InputIterator first, InputIterator last,
const Compare& x,
const Container& y);
template <class InputIterator>
priority_queue(InputIterator first, InputIterator last,
const Compare& x = Compare(),
Container&& y = Container());
Requires: x shall define a strict weak ordering ([alg.sorting]).
Effects: Initializes comp with x and c with y (copy constructing or move constructing as appropriate); calls c.insert(c.end(), first, last); and finally calls make_heap(c.begin(), c.end(), comp).
If uses_allocator_v<container_type, Alloc> is false the constructors in this subclause shall not participate in overload resolution.
template <class Alloc> explicit priority_queue(const Alloc& a);
Effects: Initializes c with a and value-initializes comp.
template <class Alloc> priority_queue(const Compare& compare, const Alloc& a);
Effects: Initializes c with a and initializes comp with compare.
template <class Alloc>
priority_queue(const Compare& compare, const Container& cont, const Alloc& a);
Effects: Initializes c with cont as the first argument and a as the second argument, and initializes comp with compare; calls make_heap(c.begin(), c.end(), comp).
template <class Alloc>
priority_queue(const Compare& compare, Container&& cont, const Alloc& a);
Effects: Initializes c with std::move(cont) as the first argument and a as the second argument, and initializes comp with compare; calls make_heap(c.begin(), c.end(), comp).
template <class Alloc> priority_queue(const priority_queue& q, const Alloc& a);
Effects: Initializes c with q.c as the first argument and a as the second argument, and initializes comp with q.comp.
template <class Alloc> priority_queue(priority_queue&& q, const Alloc& a);
Effects: Initializes c with std::move(q.c) as the first argument and a as the second argument, and initializes comp with std::move(q.comp).
void push(const value_type& x);
Effects: As if by:
c.push_back(x); push_heap(c.begin(), c.end(), comp);
Effects: As if by:
c.push_back(std::move(x)); push_heap(c.begin(), c.end(), comp);
template <class... Args> void emplace(Args&&... args)
Effects: As if by:
c.emplace_back(std::forward<Args>(args)...); push_heap(c.begin(), c.end(), comp);
Effects: As if by:
pop_heap(c.begin(), c.end(), comp); c.pop_back();
template <class T, class Container, class Compare>
void swap(priority_queue<T, Container, Compare>& x,
priority_queue<T, Container, Compare>& y) noexcept(noexcept(x.swap(y)));
Remarks: This function shall not participate in overload resolution unless is_swappable_v<Container> is true and is_swappable_v<Compare> is true.
Effects: As if by x.swap(y).