C++ Library - <priority_queue>

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The C++ Priority_queue is a container adaptor from the STL that provides the dynamic priority queue data structure. It is implemented as a binary heap, allowing efficient insertion, removal and access to the highest or lowest priority elements. By default, it orders elements in descending order based on a comparator function.Priority queues are commonly used in algorithms like Dijkstra's shortest path and Prim's minimum spanning tree.

Syntax

Below is the syntax of std::priority_queue.

template <class T, class Container = vector<T>,
class Compare = less<typename Container::value_type> < class priority_queue;

Parameters

• T − Type of the element contained.

  T may be substituted by any other data type including user-defined type.

• Container − Type of the underlying container object.

• Compare − Comparison object to be used to order the priority_queue.

  This may be a function pointer or function object that can compare its two arguments.

Member types

Following member types can be used as parameters or return type by member functions.

Sr.No.	Member types	Definition
1	value_type	T (First parameter of the template)
2	container_type	Second parameter of the template
3	size_type	size_t
4	reference	value_type&
5	const_reference	const value_type&
6	difference_type	ptrdiff_t

Functions from <priority_queue>

Below is list of all methods from <priority_queue> .

Constructors

Sr.No.	Method & Description
1	priority_queue::priority_queue default constructor Constructs an empty priority_queue with zero element.
2	priority_queue::priority_queue initialize constructor Constructs a priority_queue object and assigns internal container by a copy of ctnr.
3	priority_queue::priority_queue range constructor Constructs a priority_queue with as many elements in range of first to last.
4	priority_queue::priority_queue move constructor Constructs the priority_queue with the contents of other using move semantics.
5	priority_queue::priority_queue copy constructor Constructs a priority_queue with copy of each elements present in existing priority_queue other.

Destructor

Sr.No.	Method & Description
1	priority_queue::~priority_queue Destroys priority_queue by deallocating container memory.

Member functions

Sr.No.	Method & Description
1	priority_queue::emplace Constructs and inserts new element in sorted order in the priority_queue.
2	priority_queue::empty Tests whether pritority_queue is empty or not.
3	priority_queue::operator= Assigns new contents to the priority_queue by replacing old ones.
4	priority_queue::pop Removes front element of the priority_queue.
5	priority_queue::push Inserts new element in sorted order.
6	priority_queue::size Returns the total number of elements present in the priority_queue.
7	priority_queue::swap Exchanges the contents of priority_queue with contents of another priority_queue.
8	priority_queue::top Returns a reference to the first element of the priority_queue