STL container - basic operation of queue and deque

One .queue

1.queue The initialization

queue<Type>  name; Type It can be int,float,double,char Even structure type, etc .

queue<int>q1;
queue<double>q2;  
queue＜char＞q3;

2.queue Common functions of

Because the queue （queue） Itself is a kind of first in, first out restriction data structure , So in STL Only through  front（） To visit Team leader Elements , Or through  back（） To visit A party Elements .

push()  Insert an element at the end of the team 
pop()  Delete the first element of the queue , no return value 
size()  Return the number of elements in the queue 
empty()  If the queue is empty, return true

 Access elements ：
front()  Returns the first element in the queue 
back()  Returns the last element in the queue 

3. visit queue All elements in

    while(q.size()!=0)
    {
        cout<<q.front().name<<" ";
        deque.pop();
    }

Be careful ,queue It's a single ended queue , Not a linear structure , Iterator access and subscript access are not allowed ！ and deque（ deque ） Sure ！！

Two .deque（ deque ）

deque The container is a given type The elements of Linear processing , Like a vector , it Can access any element quickly and randomly , And it's efficient Insert and delete The tail element of the container . But it has something to do with vector Different ,deque It's a double ended array , and vector It's single ended .deque Supports efficient insertion and deletion of header elements of containers , So it's also called deque .

Deque characteristic ：

1. deque On the interface and vector Very similar , It can be directly replaced in many operation places .
2. deque Random access to elements （ Direct access to index values is supported , use [] Operator or at() Method ）
3. deque Adding or removing elements from the head and tail is very fast , But it's time-consuming to insert or remove elements in the middle .

1. initialization  

deque<Type>  name;

deque<int> deque;

2.deque Common functions of

deque.push_back(t); // Add a data at the end of the container t
deque.push_front(t); // Insert a data into the head of the container t
deque.pop_back(); // Delete the last data in the container 
deque.pop_front(); // Delete the first data of the container 
deque.size(); // Returns the number of elements in the container 
deque.empty(); // Judge whether the container is empty 
deque.clear(); // Clear queue 

3.deque Data access and element access

Data access

 First of all   Use subscript operation  deque[0] = 100;
 second   Use at  Method   Such as : deque.at(2) = 100;
 Third   The reference returned by the interface  deque.front()  and  deque.back()
 Be careful ：  The first and second methods must pay attention to cross-border !!

Element access

The first way

    while(deque.size()!=0)
    {
        cout<<deque.front().name<<" ";
        deque.pop_front();
    }

The second way （ Iterators access ）

  for(auto p=deque.begin();p!=deque.end();p++)
  {
       cout<<(*p)<<" ";
  }

The third way （ The subscript access ）

 for(int i=0;i<deque.size();i++)
 {
       cout<<deque[i]<<" ";
 }