Microsoft KB Archive/157623

= How to use priority_queue::(push,pop,empty,top) STL function in Visual C++ =

Article ID: 157623

Article Last Modified on 7/15/2005

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APPLIES TO

 The Standard C++ Library, when used with:  Microsoft Visual C++ 4.2 Enterprise Edition

 Microsoft Visual C++ 5.0 Enterprise Edition

 Microsoft Visual C++ 6.0 Enterprise Edition

 Microsoft Visual C++ 4.2 Professional Edition</li></ul>

 Microsoft Visual C++ 5.0 Professional Edition</li></ul>

 Microsoft Visual C++ 6.0 Professional Edition</li></ul>

 Microsoft Visual C++ 6.0 Standard Edition</li></ul> </li></ul>

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This article was previously published under Q157623

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

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MORE INFORMATION
The priority_queue adapter holds objects of the type defined by the type of container supported by the priority_queue. The two containers supported are the vector and the deque. Objects are inserted by push and removed by pop. top returns the top item in the priority_queue.

Since adapters do not support iteration, a priority_queue has no associated iterator.

Priority_queue allows you to maintain a sorted collection of items determined by an associated comparator function, such as less, greater, etc. The top item therefore becomes the candidate of choice, lowest or highest based on the function chosen.

Prototype
priority_queue::push; priority_queue::pop; priority_queue::empty; priority_queue::top; priority_queue::size; Note The class/parameter names in the prototype may not match the version in the header file. Sme have been modified to improve readability.

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

Sample Code
////////////////////////////////////////////////////////////////////// // // Compile options needed: /GX // // : priority_queue.cpp // // Functions: // //   priority_queue::push, priority_queue::pop, //   priority_queue::empty, priority_queue::top, queue::size // // Written by Debabrata Sarma // of Microsoft Product Support Services, // Copyright (c) 1996 Microsoft Corporation. All rights reserved. //////////////////////////////////////////////////////////////////////

using namespace std;
 * 1) include
 * 2) include
 * 3) include
 * 4) include
 * 5) include

using namespace std; // std c++ libs implemented in std #endif
 * 1) if _MSC_VER > 1020  // if VC++ version is > 4.2

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

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

// Output the item at the top using top cout << q.top << endl; // 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

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