STL Containers - difference between vector, list and deque

Question

Should I use deque instead of vector if i\'d like to push elements also in the beginning of the container? When should I use list and what\'s the point of it?

Answer 1

deque and vector provide random access, list provides only linear accesses. So if you need to be able to do container[i], that rules out list. On the other hand, you can insert and remove items anywhere in a list efficiently, and operations in the middle of vector and deque are slow.

deque and vector are very similar, and are basically interchangeable for most purposes. There are only two differences worth mentioning. First, vector can only efficiently add new items at the end, while deque can add items at either end efficiently. So why would you ever use a vector then? Unlike deque, vector guarantee that all items will be stored in contiguous memory locations, which makes iterating through them faster in some situations.

Answer 2

Use deque if you need efficient insertion/removal at the beginning and end of the sequence and random access; use list if you need efficient insertion anywhere, at the sacrifice of random access. Iterators and references to list elements are very stable under almost any mutation of the container, while deque has very peculiar iterator and reference invalidation rules (so check them out carefully).

Also, list is a node-based container, while a deque uses chunks of contiguous memory, so memory locality may have performance effects that cannot be captured by asymptotic complexity estimates.

deque can serve as a replacement for vector almost everywhere and should probably have been considered the "default" container in C++ (on account of its more flexible memory requirements); the only reason to prefer vector is when you must have a guaranteed contiguous memory layout of your sequence.