C ++中的双链表，链表和动态数组

Question

I'm new to C++ and probably these questions are so simple and basic [and sorry for that!]. Here I have two basic questions:

1. As I understand vectors in C++ are dynamic arrays. They can change size by pushing back/front elements into them.

   My question is: Are vectors allocated dynamically or the "dynamic array" name is just called because of the changing size capability? dynamically allocated array and dynamic arrays make me completely confused!

2. STL lists are linked-lists in C++ (again, as I understand). Are these doubly-linked lists or singly-linked list?

Thanks,

Answer 1

Vectors are allocated dynamically, as you can see in the mentioned documentation . You can see this better in push_back function:

If the new size() is greater than capacity() then all iterators and references (including the past-the-end iterator) are invalidated. Otherwise only the past-the-end iterator is invalidated.

Also, stick this in your mind which its complexity is amortized constant (as an instance, you can see this ).

For more info (mentioned in comments), you can find the real list as forward_list :

It is implemented as a singly-linked list and essentially does not have any overhead compared to its implementation in C. Compared to std::list this container provides more space efficient storage when bidirectional iteration is not needed.

Also, as mentioned in the documentation , list is implemented as a doubly linked list.

List containers are implemented as doubly-linked lists ; Doubly linked lists can store each of the elements they contain in different and unrelated storage locations. The ordering is kept internally by the association to each element of a link to the element preceding it and a link to the element following it.

Answer 2

1. Are vectors allocated dynamically or the "dynamic array" name is just called because of the changing size capability?

As far as I know, vectors are called dynamic arrays because their size can change at run time. But indeed, they allocate the array dynamically.

2. STL lists are linked-lists in C++ (again, as I understand). Are these doubly-linked lists or singly-linked list?

Both. list is doubly linked, and slist is singly linked. The name std::forward_list was used in stead of slist when the singly linked list was introduced to the standard library (with minor differences to the STL version).