priority_queue functions (STL Sample)

The sample code below illustrates how to use the priority_queue::push, pop, empty, and top STL functions in Visual C++.

Required Header:
<queue>

     priority_queue::push();
     priority_queue::pop();
     priority_queue::empty();
     priority_queue::top();
     priority_queue::size();

Note: The class/parameter names in the prototype do not match the version in the header file. Some have been modified to improve readability.

Description:
The sample shows priority_queue implementation using deque and vector containers.

Sample Code:

//////////////////////////////////////////////////////////////////////
//
// Compile options needed: /GX
//
// <filename> :  priority_queue.cpp
//
// Functions:
//
//    priority_queue::push(), priority_queue::pop(),
//    priority_queue::empty(), priority_queue::top(), queue::size()
//
//////////////////////////////////////////////////////////////////////

#include <iostream>
#include <queue>
#include <deque>
#include <vector>
#include <functional>

using namespace std ;

// Using priority_queue with deque
// Use of function greater sorts the items in ascending order
typedef deque<int> INTDQU;
typedef priority_queue<int> INTPRQUE;

// Using priority_queue with vector
// Use of function less sorts the items in descending order
typedef vector<char> CHVECTOR;
typedef priority_queue<char> CHPRQUE;

void main(void)
{
    int size_q;
    INTPRQUE   q;
    CHPRQUE    p;

    // Insert items in the priority_queue(uses deque)
    q.push(42);
    q.push(100);
    q.push(49);
    q.push(201);

 

Program Output is:

    // Output the size of priority_queue
    size_q = q.size();
    cout << "size of q is:" << size_q << endl;

   // Output items in priority_queue using top()
    // and use pop() to get to next item until
    // priority_queue is empty
    while (!q.empty())
    {
        cout << q.top() << endl;
        q.pop();

    }

// Insert items in the priority_queue(uses vector)
    p.push('c');
    p.push('a');
    p.push('d');
    p.push('m');
    p.push('h');

    // Output the item at the top using top()
    cout << p.top() << endl;

    // Output the size of priority_queue
    size_q = p.size();
    cout << "size of p is:" << size_q << endl;

    // Output items in priority_queue using top()
    // and use pop() to get to next item until
    // priority_queue is empty
    while (!p.empty())
    {
        cout << p.top() << endl;
        p.pop();

    }
}

Program Output:

42
size of q is:4
42
49
100
201
m
size of p is:5
m
h
d
c
a