197 lines
4.6 KiB
Markdown
197 lines
4.6 KiB
Markdown
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---
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title: queue
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localeTitle: 队列
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---
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## 队列
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`queue`是C ++中最常用的容器之一。容器是一种存储对象集合的数据结构,有些是有序的,有些则不是。所有容器都有一组不同的功能,允许您访问该集合中的对象。
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`std::queue`是C ++标准库的一部分(因此前缀为`std::` ,允许您以先入先出(FIFO)顺序存储数据。注意: **队列中的所有对象必须具有相同的数据类型**
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存储在队列中的数据类型位于queue关键字旁边的尖括号内。例如,如果要存储整数集合,则队列将为`std::queue<int> queue_name`
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### 队列LIFO解释
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`queue`允许我们按特定顺序推送/排队和弹出/出列。 **推送**意味着在队列的前面插入一个对象。 **Pop**意味着从队列末尾拉出“最旧的”对象。所以当你推动它在前面时,当你弹出时,你提取最旧的元素。
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![alt text](https://github.com/mohammadaziz313/helloworld/blob/master/Fifo_queue.png "FIFO队列入队和出队示例")
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### 队列操作
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队列容器支持以下操作:
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* 推(入队)
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* pop(出队)
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* 空
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* 尺寸
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* 面前
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* 背部
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#### 推
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允许您在队列末尾的当前最后一个元素之后插入一个新元素。
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```cpp
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//Push operation in Queue
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#include <iostream> // std::cout
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#include <queue> // std::queue
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int main ()
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{
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std::queue<int> q;
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q.push(1); //Pushing 1 at front of the queue
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q.push(2); //Pushing 2 at front of the queue
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return 0;
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}
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```
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#### 面前
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允许您访问队列中的下一个元素而不删除它。 下一个元素是队列中“最旧的”元素。
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```cpp
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//Front operation in Queue
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#include <iostream> // std::cout
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#include <queue> // std::queue
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int main ()
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{
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std::queue<int> q;
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q.push(1); //Pushing 1 at front of the queue
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q.push(2); //Pushing 2 at front of the queue
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std::cout<<q.front()<<'\n'; //Accessing the front of the queue
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std::cout<<q.front()<<'\n'; //Accessing the front of the queue
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return 0;
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}
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```
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```
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Output:
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1
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1
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```
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#### 流行的
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允许您删除队列中的下一个元素,有效地将其大小减小一个。 删除的元素是“最旧的”元素。
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```cpp
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//Pop operation in Queue
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#include <iostream> // std::cout
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#include <queue> // std::queue
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int main ()
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{
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std::queue<int> q;
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q.push(1); //Pushing 1 at front of the queue
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q.push(2); //Pushing 2 at front of the queue
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std::cout<<q.front()<<'\n'; //Accessing the front of the queue
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q.pop(); //Removing the oldest element
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std::cout<<q.front()<<'\n'; //Accessing the front of the queue
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q.pop(); //Removing the oldest element
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return 0;
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}
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```
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```
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Output:
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1
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2
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```
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#### 尺寸
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返回`queue`的元素数。
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```cpp
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//Size operation in Queue
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#include <iostream> // std::cout
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#include <queue> // std::queue
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int main ()
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{
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std::queue<int> q;
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q.push(1); //Pushing 1 at front of the queue
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q.push(2); //Pushing 2 at front of the queue
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std::cout<<q.size()<<'\n'; //Accessing the front of the queue
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q.pop(); //Removing the oldest element
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std::cout<<q.size()<<'\n'; //Accessing the front of the queue
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q.pop(); //Removing the oldest element
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std::cout<<q.size()<<'\n'; //Accessing the front of the queue
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return 0;
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}
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```
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```
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Output:
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2
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1
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0
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```
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#### 空
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返回`queue`是否为空,即队列大小是否为零。 如果队列的大小为0,则返回`true` ,否则返回`false`
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\`\`\`cpp //队列中的空操作
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# 包括 // std :: cout
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# 包括 // std :: stack
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int main() { 的std ::队列 q;
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q.push(1); q.push(2);
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while(q.empty()!= true){ 的std :: COUT << q.front()<< '\\ n'; q.pop(); }
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std :: cout <<“Out of loop”<<'\\ n'; 返回0; }
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```
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Output:
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1
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2
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Out of loop
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#### Back
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Allows you to access the last element in the queue without removing it.
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The next element is the "newest" element in the queue.
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```
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CPP //在队列中返回操作
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# 包括 // std :: cout
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# 包括 // std :: queue
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int main() { 的std ::队列 q;
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q.push(1); //在队列前面按1 q.push(2); //在队列前面按2
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的std :: COUT << q.back()<< '\\ n'; //访问队列的后面 的std :: COUT << q.back()<< '\\ n'; //访问队列的后面
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返回0; } \`\`\`
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```
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Output:
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2
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2
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```
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### 更多资源:
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http://www.cplusplus.com/reference/queue/queue/
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### 引文:
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图片礼貌:https _:_ //en.wikipedia.org/wiki/FIFO _(computing_ and\_electronics)
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