• 元素类型C++ 标准模板库STL 队列 queue 使用方法与应用介绍(一)


    发一下牢骚和主题无关:

        queue

        queue模板类的定义在<queue>头文件中。

        与stack模板类很相似,queue模板类也需要两个模板参数,一个是元素类型,一个容器类型,元素类型是必要的,容器类型是可选的,默以为deque类型。

        定义queue对象的示例代码如下:

        queue<int> q1;

        queue<double> q2;

        queue的基本操作有:

        

        入队,如例:q.push(x); 将x接到队列的末了。

        出队,如例:q.pop(); 弹出队列的第一个元素,注意,并不会返回被弹出元素的值。

        拜访队首元素,如例:q.front(),即最早被压入队列的元素。

        拜访队尾元素,如例:q.back(),即最后被压入队列的元素。

        判断队列空,如例:q.empty(),当队列空时,返回true。

        拜访队列中的元素个数,如例:q.size()

        

        

        

    std::queue

        

    FIFO queue

        

        queue

        

        s are a type of container adaptor, specifically designed to operate in a FIFO context (first-in first-out), where elements are inserted into one end of the container and extracted from the other.

        

        queue

        

        s are implemented as

        

        containers adaptors

        

        , which are classes that use an encapsulated object of a specific container class as its

        

        underlying container

        

        , providing a specific set of member functions to access its elements. Elements are

        

        pushed

        

        into the

        

        "back"

        

        of the specific container and

        

        popped

        

        from its

        

        "front"

        

        .

        The underlying container may be one of the standard container class template or some other specifically designed container class. The only requirement is that it supports the following operations:

        

    • front()
    • back()
    • push_back()
    • pop_front()

        Therefore, the standard container class templates

         deque

        and

        list

        can be used. By default, if no container class is specified for a particular

        

        queue

        

        class, the standard container class template

         deque

        is used.

        In their implementation in the C++ Standard Template Library, queues take two template parameters:

     
    template < class T, class Container = deque<T> > class queue;

    Where the template parameters have the following meanings:

        

    • T: Type of the elements.
    • Container: Type of the underlying container object used to store and access the elements.

        In the reference for the queue member functions, these same names are assumed for the template parameters.

         

        

        

        每日一道理
    宽容,是一种坦荡,可以无私无畏,无拘无束,无尘无染。宽容,是一种豁达,是比海洋和天空更为博大的胸襟,是宽广和宽厚的叠加,延续和升华。宽容有度,宽容无价,宽以待人,这是人生处世的基本法则。
    #include <iostream>
    #include <queue>
    #include <string>
    using namespace std;
    void test_empty()
    {
      queue<int> myqueue;
      int sum (0);
    
      for (int i=1;i<=10;i++) myqueue.push(i);
    
      while (!myqueue.empty())
      {
         sum += myqueue.front();
         myqueue.pop();
      }
        cout << "total: " << sum << endl;
    }//运行结果: total: 55
    void test_pop()
    {
      queue<int> myqueue;
      int myint;
    
      cout << "\nPlease enter some integers (enter 0 to end):\n";
    
      do
      {
        cin >> myint;
        myqueue.push (myint);
      } while (myint);
    
      cout << "myqueue contains: ";
      while (!myqueue.empty())
      {
        cout << " " << myqueue.front();
        myqueue.pop();
      }
    }
    /********
    运行结果:
    Please enter some integers (enter 0 to end):
    512
    605
    420
    517
    532
    0
    myqueue contains:  512 605 420 517 532 0
    ********/
    void test_size()
    {
      queue<int> myints;
      cout << "0. size: " << (int) myints.size() << endl;
    
      for (int i=0; i<5; i++) myints.push(i);
      cout << "1. size: " << (int) myints.size() << endl;
    
      myints.pop();
      cout << "2. size: " << (int) myints.size() << endl;
    }
    /****
    运行结果:
    0. size: 0
    1. size: 5
    2. size: 4
    ****/
    int main()
    {
        test_empty();
        cout<<"\n***********************************************\n";
        test_size();
        cout<<"\n***********************************************\n";
        test_pop();
        cout<<"\n***********************************************\n";
        queue<string> q;
    
        // insert three elements into the queue
        q.push("These ");
        q.push("are ");
        q.push("more than ");
        //cout << "number of elements in the queue: " << q.size()<< endl;
    
        // read and print two elements from the queue
        cout << q.front();
        q.pop();
        cout << q.front();
        q.pop();
        //cout << "number of elements in the queue: " << q.size()<< endl;
    
        // insert two new elements
        q.push("four ");
        q.push("words!");
        //cout << "\nnumber of elements in the queue: " << q.size()<< endl;
        // skip one element
        q.pop();
    
        // read and print two elements
        cout << q.front();
        q.pop();
        cout << q.front() << endl;
        q.pop();
    
        // print number of elements in the queue
        cout << "number of elements in the queue: " << q.size()<< endl;
    }
    /*******
    *运行结果:
    total: 55
    
    ***********************************************
    0. size: 0
    1. size: 5
    2. size: 4
    
    ***********************************************
    
    Please enter some integers (enter 0 to end):
    512
    605
    420
    517
    532
    0
    myqueue contains:  512 605 420 517 532 0
    ***********************************************
    These are four words!
    number of elements in the queue: 0
    
    Process returned 0 (0x0)   execution time : 33.512 s
    Press any key to continue.
    
    ********/

    文章结束给大家分享下程序员的一些笑话语录: 开发时间
      项目经理: 如果我再给你一个人,那可以什么时候可以完工?程序员: 3个月吧!项目经理: 那给两个呢?程序员: 1个月吧!
    项目经理: 那100呢?程序员: 1年吧!
    项目经理: 那10000呢?程序员: 那我将永远无法完成任务.

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  • 原文地址:https://www.cnblogs.com/xinyuyuanm/p/3080511.html
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