queue container

queue container

Queue Basic Concepts

Concept: A Queue is a First In First Out (FIFO) data structure, which has two ends.

Queue container allows adding elements from one end and removing elements from the other end.

In a queue, only the head and tail are accessible to external operations, which means that queue does not permit traversal behavior.

Adding data to a queue is called --- enqueue push

Removing data from a queue is called --- dequeue pop

Queues in Life:

Common interfaces for queue

Function Description: Common public interfaces for stack container

Constructor:

• queue<T> que; //queue is implemented using template classes, the default constructor form for queue objects
• queue(const queue &que); //copy constructor

Assignment operation:

• queue& operator=(const queue &que); //overloading the equality operator

Data Access:

• push(elem); //add elements to the end of the queue
• pop(); //Remove the first element from the front of the queue
• back(); //Returns the last element
• front(); //return the first element

Size Operations:

• empty(); //Check if the stack is empty
• size(); //return stack size

Example:

#include <iostream>
#include <queue>
#include <string>

using namespace std;

class Person
{
public:
    Person(string name, int age)
    {
        this->m_Name = name;
        this->m_Age = age;
    }

    string m_Name;
    int m_Age;
};

void test01() {

    //创建队列
    queue<Person> q;

    //准备数据
    Person p1("唐僧", 30);
    Person p2("孙悟空", 1000);
    Person p3("猪八戒", 900);
    Person p4("沙僧", 800);

    //向队列中添加元素  入队操作
    q.push(p1);
    q.push(p2);
    q.push(p3);
    q.push(p4);

    //队列不提供迭代器，更不支持随机访问 
    while (!q.empty()) {
        //输出队头元素
        cout << "队头元素-- 姓名： " << q.front().m_Name 
              << " 年龄： "<< q.front().m_Age << endl;
        
        cout << "队尾元素-- 姓名： " << q.back().m_Name  
              << " 年龄： " << q.back().m_Age << endl;
        
        cout << endl;
        //弹出队头元素
        q.pop();
    }

    cout << "队列大小为：" << q.size() << endl;
}

int main() {

    test01();


    return 0;
}

运行结果：

队头元素-- 姓名： 唐僧 年龄： 30
队尾元素-- 姓名： 沙僧 年龄： 800

队头元素-- 姓名： 孙悟空 年龄： 1000
队尾元素-- 姓名： 沙僧 年龄： 800

队头元素-- 姓名： 猪八戒 年龄： 900
队尾元素-- 姓名： 沙僧 年龄： 800

队头元素-- 姓名： 沙僧 年龄： 800
队尾元素-- 姓名： 沙僧 年龄： 800

队列大小为：0

Summary:

• Enqueue --- push
• dequeue --- pop
• Return the front element --- front
• Return the element at the back of the queue --- back
• Check if the queue is empty --- empty
• Return queue size --- size