Methods of Priority Queue
The following list of all the methods of std::priority_queue class:
|
Method |
Definition |
|---|---|
| priority_queue::empty() | Returns whether the queue is empty. |
| priority_queue::size() | Returns the size of the queue. |
| priority_queue::top() | Returns a reference to the topmost element of the queue. |
| priority_queue::push() | Adds the element ‘g’ at the end of the queue. |
| priority_queue::pop() | Deletes the first element of the queue. |
| priority_queue::swap() | Used to swap the contents of two queues provided the queues must be of the same type, although sizes may differ. |
| priority_queue::emplace() | Used to insert a new element into the priority queue container. |
| priority_queue value_type | Represents the type of object stored as an element in a priority_queue. It acts as a synonym for the template parameter. |
Priority Queue in C++ Standard Template Library (STL)
A C++ priority queue is a type of container adapter, specifically designed such that the first element of the queue is either the greatest or the smallest of all elements in the queue, and elements are in non-increasing or non-decreasing order (hence we can see that each element of the queue has a priority {fixed order}).
In C++ STL, the top element is always the greatest by default. We can also change it to the smallest element at the top. Priority queues are built on the top of the max heap and use an array or vector as an internal structure. In simple terms, STL Priority Queue is the implementation of Heap Data Structure.
Syntax:
std::priority_queue<int> pq;
Example:
C++
// C++ program to demonstrate the use of priority_queue#include <iostream>#include <queue>using namespace std;// driver codeint main(){ int arr[6] = { 10, 2, 4, 8, 6, 9 }; // defining priority queue priority_queue<int> pq; // printing array cout << "Array: "; for (auto i : arr) { cout << i << ' '; } cout << endl; // pushing array sequentially one by one for (int i = 0; i < 6; i++) { pq.push(arr[i]); } // printing priority queue cout << "Priority Queue: "; while (!pq.empty()) { cout << pq.top() << ' '; pq.pop(); } return 0;} |
Array: 10 2 4 8 6 9 Priority Queue: 10 9 8 6 4 2
Max Heap Priority Queue (default scheme)