queue container

1.queue container

1.1.Basic concepts of queues

Concept:Queue is a kind ofFirst In First Out(First In First Out, FIFO) data structure, it has two exits

A queue container allows adding elements at one end and removing elements from the other end.

Only the front and rear of the queue can be accessed externally; therefore, the queue does not permit traversal behavior.

Inserting data into a queue is called --- enqueue push

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

Queues in life:

1.2.Common queue interfaces

Function description: common external interfaces of the stack container

Constructor:

• queue<T> que; // The queue is implemented as a template class, and the default constructor form of a queue object is
• queue(const queue &que); // copy constructor

Assignment operation:

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

Data Access:

• push(elem); // Add an element to the tail of the queue
• pop(); // Remove the first element from the head of the queue
• back(); // Return the last element
• front(); // Return the first element

Size operations:

• empty(); // Determine whether the stack is empty
• size(); // Return the size of the stack

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;
}

Operation result:

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 back element --- back
• Determine whether the queue is empty --- empty
• Return the queue size --- size