STL series ----- deque container details

1, the basic concept

Function: double-ended array , can be inserted into the head end of the deletion

deque and vector difference:

vector for the low efficiency for the head insertion and deletion , the greater the amount of data, the less efficient the
deque contrast, insertion and deletion of vector faster than the speed of the head
will be faster than the access speed deque element vector, both of which inner and implemented related

Iterator deque container also supports random access

2, constructors

The default constructor form

deque<T>  deqT

Constructor [beg, end) section of the copy to the elements themselves.

deque（beg，end）

The constructor of n elem copy to itself.

deque（n，elem）

Copy constructor

deque（const deque& deq）

If you want to limit the data is read-only state, then the state must also change the iterator

#include<iostream>
using namespace std;
#include<deque>
void printDeque(const deque<int>&d)
{
 for(deque<int>::const_iterator it=d.begin();it!=d.end();it++)
 {
  cout<<*it<<" ";
 }
 cout<<endl;
}
void test01()
{
 //无参构造，默认构造 
 deque<int>d1;
    for(int i=0;i<10;i++)
    {
     d1.push_back(i);
 }
 printDeque(d1);
 //第二种
 deque<int>d2(d1.begin(),d1.end()) ;
 printDeque(d2);
 //第三种
 deque<int>d3(10,100) ;
 printDeque(d3);
 //第四种
 deque<int>d4(d3); 
 printDeque(d4);
}
int main()
{
    test01();
}

deque and vector container configured almost the same manner

3, assignment

Equality operator overloading

vector& operator=（const vector&vec）

The [beg, end) copy of the data interval is assigned to itself

assign（beg，end）

The n copies assigned to itself elem

assign（n，elem）；

code show as below

#include<iostream>
using namespace std;
#include<deque>
void printDeque(const deque<int>&d)
{
 for(deque<int>::const_iterator it=d.begin();it!=d.end();it++)
 {
  cout<<*it<<" ";
 }
 cout<<endl;
}
void test01()
{
 deque<int>d1;
    for(int i=0;i<10;i++)
    {
     d1.push_back(i);
 }
 printDeque(d1);
 //第一种
 deque<int>d2; 
 d2=d1;
 printDeque(d2);
 //第二种 
 deque<int>d3;
 d3.assign(d1.begin(),d1.end()) ;
 printDeque(d3);
 //第三种
 deque<int>d4;
 d4.assign(10,100);
 printDeque(d4);
 
}
int main()
{
    test01();
}

4, the capacity, the size of the operation

For determining the size and capacity of the container deque

Determining whether the container is empty

empty（）

Returns the number of elements of the container

size（）

The length of the container is re-designated num

resize（int num）

If the container becomes long, filled with new values ​​in a default position. If the container becomes short, the elements of the container beyond the end of the length are deleted.
 

The length of the container is re-designated num

resize（int num，elem）；

If the container becomes longer, the value to fill the new position places elem. If the container becomes short, the elements of the container does not exceed the length of the tail is removed

deque no capacity concept, but the size of the concept
because it is an array of double-ended

code show as below

#include<iostream>
using namespace std;
#include<deque>
void printDeque(deque<int>&d)
{
 for(deque<int>::iterator it=d.begin();it!=d.end();it++)
 {
  cout<<*it<<" ";
 }
 cout<<endl;
}
void test01()
{
 deque<int>d1;
    for(int i=0;i<10;i++)
    {
     d1.push_back(i);
 }
 printDeque(d1);
 if(d1.empty())
 {
  cout<<"d1为空"<<endl;
 }
 else
 {
  cout<<"d1不为空"<<endl;
  cout<<"d1的大小为:"<<d1.size()<<endl;
 }
 //重新指定大小 
 d1.resize(15,2);
 printDeque(d1);
 d1.resize(5);
 printDeque(d1);
}
int main()
{
    test01();
}

to sum up:

deque no capacity concept

Determine whether an empty ------ empty

The number of elements ----------- size Returns

Reassign the number ------------ resize

5, insert and delete

Deque to insert and delete data

Prototype:

Add a data container in the tail

push_back（elem）；

Inserting a container header data

push_front（elem）

Delete the last data container

pop_back（）

Delete the first container data

pop_front（）

Specifies the position of the operation:
insert a copy of the position pos elem element, the return position of the new data

insert（pos，elem）

Inserts n elem data position pos, no return value.

insert（pos，n，elem）

在pos位置插入[beg.end）区间的数据，无返回值。

insert（pos，beg，end）

清空容器的所有数据

clear（）

删除[beg.end）区间的数据，返回下一个数据的位置。

erase（beg，end）

删除pos位置的数据，返回下一个数据的位置。

erase（pos）

其中，pos都是迭代器
代码如下

#include<iostream>
using namespace std;
#include<deque>
void printDeque(deque<int>&d)
{
 for(deque<int>::iterator it=d.begin();it!=d.end();it++)
 {
  cout<<*it<<" ";
 }
 cout<<endl;
}
//两端操作 
void test01()
{
 deque<int> d;
 //尾插 
 d.push_back(10);
 d.push_back(20);
 //头插 
 d.push_front(100);
 d.push_front(200);
 //200 100 10 20
 printDeque(d); 
 //尾删
 d.pop_back();
 //200 100 10
 printDeque(d);
 //头删
 d.pop_front();
 //100 10
 printDeque(d);
}
void test02()
{
 deque<int> d;
 d.push_back(10);
 d.push_back(20);
 d.push_front(100);
 d.push_front(200);
 //200 100 10 20
 printDeque(d); 
 d.insert(d.begin(),1000); 
 //1000,200 100 10 20
 printDeque(d); 
 d.insert(d.begin(),2,1000); 
 //1000,1000,1000,200 100 10 20
 printDeque(d); 
 //指定位置插入区间
 deque<int> d2;
 d2.push_back(1);
 d2.push_back(2);
 d2.push_front(10);
 d2.push_front(20);
 d.insert(d.begin(),d2.begin(),d2.end());
 printDeque(d); 
}
void test03()
{
 deque<int> d;
 d.push_back(10);
 d.push_back(20);
 d.push_front(100);
 d.push_front(200);
 //200 100 10 20
 printDeque(d); 
 d.erase(d.begin());
 //100 10 20
 printDeque(d); 
 //删除指定项
 deque<int>::iterator it=d.begin();
 it++;
 d.erase(it);
 printDeque(d); 
 //清空
 //d.clear();
 d.erase(d.begin(),d.end());
 printDeque(d); 
}
int main()
{
    //test01();
    //test02();
    test03();
}

6、数据存取

返回索引idx所指的数据

at（int idx）

返回索引idx所指的数据

operator[]

返回容器中第一个数据元素

front（）

返回容器中最后一个数据元素

back（）

代码如下

#include<iostream>
using namespace std;
#include<deque>
void printDeque(deque<int>&d)
{
 for(deque<int>::iterator it=d.begin();it!=d.end();it++)
 {
  cout<<*it<<" ";
 }
 cout<<endl;
}
//两端操作 
void test01()
{
 deque<int> d;
 d.push_back(10);
 d.push_back(20);
 d.push_front(100);
 d.push_front(200);
 printDeque(d);
 for(int i=0;i<d.size();i++)
 {
  cout<<d[i]<<" ";
 }
 cout<<endl;
 for(int i=0;i<d.size();i++)
 {
  cout<<d.at(i)<<" ";
 }
 cout<<endl;
 cout<<"第一个元素为："<<d.front()<<endl;
 cout<<"最后一个元素为："<<d.back()<<endl;
}
int main()
{
    test01();
}

7、排序

对beg和end区间内元素进行排序

sort（iterator    beg，iterator   end）

代码如下

#include<iostream>
using namespace std;
#include<deque>
#include<algorithm>
void printDeque(deque<int>&d)
{
 for(deque<int>::iterator it=d.begin();it!=d.end();it++)
 {
  cout<<*it<<" ";
 }
 cout<<endl;
}
//两端操作 
void test01()
{
 deque<int> d;
 d.push_back(10);
 d.push_back(20);
 d.push_front(100);
 d.push_front(200);
 printDeque(d);
 cout<<"排序后:"<<endl;
 sort(d.begin(),d.end());
 printDeque(d);
}
int main()
{
    test01();
}

默认sort都是升序排序，也可以添加函数改为降序排序