[C++] Study Notes (6)----deque container

deque container

container: deque
head File: #include<deque>

Basic concept of deque container

Function

• Double-ended array, which can perform insertion and deletion operations on the head end

The difference between deque and vector:

• The insertion and deletion efficiency of vector for the head is low, and the larger the data volume, the lower the efficiency
• Relatively speaking, deque will insert and delete the head faster than vector
• Vector accesses elements faster than deque, which is related to the internal implementation of the two

The inner working principle of deque:

There is a central controller inside the deque , which maintains the contents of each buffer, and stores real data in the buffer

The central controller maintains the address of each buffer, making deque like a continuous memory space

• The iterator of the deque container also supports random access

deque constructor

function prototype

• deque<T> deqT;//Default construction form
• deque(beg, end);//The constructor copies the elements in the range [beg, end] to itself
• deque(n, elem);//The constructor copies n elems to itself
• deque(const deque &deq);//copy constructor

deque assignment operation

function prototype

• deque& operator=(const deque &deq);// Overload the equals operator
• assign(beg, end);// Assign the data copy in the [beg, end] range to itself
• assign(n, elem);// Assign n elem copies to itself

deque size operation

function prototype

• deque.empty();// Check if the container is empty

• deque.size();//returns the number of elements in the container

• deque.resize(num);//Respecify the length of the container as num, if the container becomes longer, fill the new position with the default value

  // If the container becomes shorter, the elements at the end that exceed the length of the container are deleted

• deque.resize(num, elem);//Respecify the length of the container as num, if the container becomes longer, fill the new position with elem value

  // If the container becomes shorter, the elements at the end that exceed the length of the container are deleted

deque insertion and deletion

function prototype

Insert operation at both ends:

• push_back(elem);//Add a data at the end of the container

• push_front(elem);//Insert a data at the head of the container

• pop_back();//Delete the last data in the container

• pop_front();//Delete the first data in the container

Specified position operation:

• insert(pos, elem);//Insert a copy of the elem element at position pos and return the position of the new data
• insert(pos, n, elem);//Insert n elem data at pos position, no return value
• insert(pos, beg, end);//Insert the data in [beg, end] range at position pos, no return value
• clear();// Clear all data in the container
• erase(beg, end);//Delete the data in the interval [beg, end] and return the position of the next data
• erase(pos);//Delete the data at position pos and return the position of the next data

deque data access

function prototype

• at(int idx);//Return the data pointed to by the index idx
• operator[];//Return the data pointed to by the index idx
• front();//returns the first data element in the container
• back();//returns the last data element in the container

deque sorting

Functional description

• Using algorithms to sort deque containers

algorithm

• sort(iterator beg, iterator end);//Sort the elements in the range of beg and end (header file #include<algorithm>) The default sorting rules are ascending order from small to large

For containers that support random access iterators, the sort algorithm can be used to sort them directly