Use the member functions of the STL queue class in Visual C++

The sample code below illustrates how to use the queue::push, queue::pop, queue::empty, queue::back, queue::front, and queue::size STL functions in Visual C++. The information in this article applies to unmanaged Visual C++ code only.

Original product version:   Visual C++
Original KB number:   157622

Summary

The queue adapter holds objects of the type defined by the type of container supported by the queue. The two containers supported are the list and the deque. Objects are inserted by push() and removed by pop(). front() returns the oldest item in the queue (also known as FIFO), and back() returns the latest item inserted in the queue.

Required header

• <queue>

Prototypes

queue::push();
queue::pop();
queue::empty();
queue::back();
queue::front();
queue::size();

Sample code

The sample shows queue implementation using list and deque containers.

//////////////////////////////////////////////////////////////////////
// Compile options needed: none
// <filename> : queue.cpp
// Functions:
// queue::push(), queue::pop(), queue::empty(), queue::back(),
// queue::front(),queue::size()
// Copyright (c) 1996 Microsoft Corporation. All rights reserved.
//////////////////////////////////////////////////////////////////////

/* Compile options needed: /GX */
#include <list>
#include <iostream>
#include <queue>
#include <deque>
using namespace std;

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

// Using queue with list
typedef list<int, allocator<int>> INTLIST;
typedef queue<int, INTLIST> INTQUEUE;

// Using queue with deque
typedef deque<char *, allocator<char *>> CHARDEQUE;
typedef queue<char *, CHARDEQUE> CHARQUEUE;
void main(void)
{
    int size_q;
    INTQUEUE q;
    CHARQUEUE p;

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

    // Output the item inserted last using back()
    cout << q.back() << endl;

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

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

    // Insert items in the queue(uses deque)
    p.push("cat");
    p.push("ape");
    p.push("dog");
    p.push("mouse");
    p.push("horse");

    // Output the item inserted last using back()
    cout << p.back() << endl;

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

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

Program output

201
size of q is:4
42
100
49
201
horse
size of p is:5
cat
ape
dog
mouse
horse

References

For the same information about member functions of the STL queue class, see queue.