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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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.
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Required header
<queue>
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Prototype
priority_queue::push();
priority_queue::pop();
priority_queue::empty();
priority_queue::top();
priority_queue::size();
The class/parameter names in the prototype may not match the
version in the header file. Sme have been modified to improve readability.
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Description
The sample shows priority_queue implementation using deque and
vector containers.
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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()
//
// Written by Debabrata Sarma
// of Microsoft Product Support Services,
// Copyright (c) 1996 Microsoft Corporation. All rights reserved.
//////////////////////////////////////////////////////////////////////
#include <iostream>
#include <queue>
#include <deque>
#include <vector>
#include <functional>
using namespace std;
#if _MSC_VER > 1020 // if VC++ version is > 4.2
using namespace std; // std c++ libs implemented in std
#endif
// Using priority_queue with deque
// Use of function greater sorts the items in ascending order
typedef deque<int, allocator<int> > INTDQU;
typedef priority_queue<int,INTDQU, greater<int> > INTPRQUE;
// Using priority_queue with vector
// Use of function less sorts the items in descending order
typedef vector<char, allocator<char> > CHVECTOR;
typedef priority_queue<char,CHVECTOR,less<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);
// 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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For the same topic about the queue functions, visit the
following MSDN Web site:
http://msdn.microsoft.com/library/en-us/vclang98/html/sample_queue_functions_(STL_Sample).asp?frame=true (http://msdn.microsoft.com/library/en-us/vclang98/html/sample_queue_functions_(STL_Sample).asp?frame=true)Back to the top
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