> For the complete documentation index, see [llms.txt](https://cui-jiacai.gitbook.io/c++-stl-tutorial/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://cui-jiacai.gitbook.io/c++-stl-tutorial/rong-qi-container/queue-dui-lie.md).

# queue - 队列

## queue 容器基本概念

queue 是一种先进先出(First In First Out, FIFO)的数据结构，它有两个出口，queue容器允许从一端新增元素，从另一端移除元素。

![queue](/files/4GcIcNMBg6sd3D7ijaWG)

## queue 没有迭代器

只有queue的顶端元素，才有机会被外界去用。queue不提供遍历功能，也不提供迭代器。

## queue 常用API

### queue 构造函数

```cpp
queue<T> queT; // queue对象的默认构造函数形式，采用模版类实现
queue(const queue& que); // 拷贝构造函数
```

### queue 存取、插入和删除操作

```cpp
void push(T elem); // 往队尾添加元素
void pop(); // 从队头移除第一个元素
T& back(); // 返回最后一个元素
T& front(); // 返回第一个元素
```

### queue 赋值操作

```cpp
queue& operator=(const queue& que); // 重载赋值操作符
```

### queue 大小操作

```cpp
bool empty(); // 判断队列是否为空
int size(); // 返回队列的大小
```

{% hint style="success" %}
至此，读者应当对queue的特点及基本操作有了较为全面的认识，使用时API记不清可以回头多看。
{% endhint %}


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