What is a container in C++

 Standard ContainersA container is a holder object that stores a collection of other objects (its elements). They are implemented as class templates, which allows a great flexibility in the types supported as elements.

The container manages the storage space for its elements and provides member functions to access them, either directly or through iterators (reference objects with similar properties to pointers).

Containers replicate structures very commonly used in programming: dynamic arrays (vector), queues (queue), stacks (stack), heaps (priority_queue), linked lists (list), trees (set), associative arrays (map)…

Many containers have several member functions in common, and share functionalities. The decision of which type of container to use for a specific need does not generally depend only on the functionality offered by the container, but also on the efficiency of some of its members (complexity). This is especially true for sequence containers, which offer different trade-offs in complexity between inserting/removing elements and accessing them.

stack, queue and priority_queue are implemented as container adaptors. Container adaptors are not full container classes, but classes that provide a specific interface relying on an object of one of the container classes (such as deque or list) to handle the elements. The underlying container is encapsulated in such a way that its elements are accessed by the members of the container adaptor independently of the underlying container class used.

Container class templates

Sequence containers:
array Array class (class template )vectorVector (class template )dequeDouble ended queue (class template )forward_list Forward list (class template )listList (class template )
Container adaptors:
stackLIFO stack (class template )queueFIFO queue (class template )priority_queuePriority queue (class template )
Associative containers:
setSet (class template )multisetMultiple-key set (class template )mapMap (class template )multimapMultiple-key map (class template )
Unordered associative containers:
unordered_set Unordered Set (class template )unordered_multiset Unordered Multiset (class template )unordered_map Unordered Map (class template )unordered_multimap Unordered Multimap (class template )
Other:
Two class templates share certain properties with containers, and are sometimes classified with them: bitset and valarray.

Member map

This is a comparison chart with the different member functions present on each of the different containers:

Legend:

C++98	Available since C++98
C++11	New in C++11

Sequence containers

Headers	<array>	<vector>	<deque>	<forward_list>	<list>
Members	array	vector	deque	forward_list	list
	constructor	implicit	vector	deque	forward_list	list
destructor	implicit	~vector	~deque	~forward_list	~list
operator=	implicit	operator=	operator=	operator=	operator=
iterators	begin	begin	begin	begin	begin before_begin	begin
end	end	end	end	end	end
rbegin	rbegin	rbegin	rbegin		rbegin
rend	rend	rend	rend		rend
const iterators	cbegin	cbegin	cbegin	cbegin	cbegin cbefore_begin	cbegin
cend	cend	cend	cend	cend	cend
crbegin	crbegin	crbegin	crbegin		crbegin
crend	crend	crend	crend		crend
capacity	size	size	size	size		size
max_size	max_size	max_size	max_size	max_size	max_size
empty	empty	empty	empty	empty	empty
resize		resize	resize	resize	resize
shrink_to_fit		shrink_to_fit	shrink_to_fit
capacity		capacity
reserve		reserve
element access	front	front	front	front	front	front
back	back	back	back		back
operator[]	operator[]	operator[]	operator[]
at	at	at	at
modifiers	assign		assign	assign	assign	assign
emplace		emplace	emplace	emplace_after	emplace
insert		insert	insert	insert_after	insert
erase		erase	erase	erase_after	erase
emplace_back		emplace_back	emplace_back		emplace_back
push_back		push_back	push_back		push_back
pop_back		pop_back	pop_back		pop_back
emplace_front			emplace_front	emplace_front	emplace_front
push_front			push_front	push_front	push_front
pop_front			pop_front	pop_front	pop_front
clear		clear	clear	clear	clear
swap	swap	swap	swap	swap	swap
list operations	splice				splice_after	splice
remove				remove	remove
remove_if				remove_if	remove_if
unique				unique	unique
merge				merge	merge
sort				sort	sort
reverse				reverse	reverse
observers	get_allocator		get_allocator	get_allocator	get_allocator	get_allocator
data	data	data

Associative containers

Headers	<set>	<map>	<unordered_set>	<unordered_map>
Members	set	multiset	map	multimap	unordered_set	unordered_multiset	unordered_map	unordered_multimap
	constructor	set	multiset	map	multimap	unordered_set	unordered_multiset	unordered_map	unordered_multimap
destructor	~set	~multiset	~map	~multimap	~unordered_set	~unordered_multiset	~unordered_map	~unordered_multimap
assignment	operator=	operator=	operator=	operator=	operator=	operator=	operator=	operator=
iterators	begin	begin	begin	begin	begin	begin	begin	begin	begin
end	end	end	end	end	end	end	end	end
rbegin	rbegin	rbegin	rbegin	rbegin
rend	rend	rend	rend	rend
const iterators	cbegin	cbegin	cbegin	cbegin	cbegin	cbegin	cbegin	cbegin	cbegin
cend	cend	cend	cend	cend	cend	cend	cend	cend
crbegin	crbegin	crbegin	crbegin	crbegin
crend	crend	crend	crend	crend
capacity	size	size	size	size	size	size	size	size	size
max_size	max_size	max_size	max_size	max_size	max_size	max_size	max_size	max_size
empty	empty	empty	empty	empty	empty	empty	empty	empty
reserve					reserve	reserve	reserve	reserve
element access	at			at				at
operator[]			operator[]				operator[]
modifiers	emplace	emplace	emplace	emplace	emplace	emplace	emplace	emplace	emplace
emplace_hint	emplace_hint	emplace_hint	emplace_hint	emplace_hint	emplace_hint	emplace_hint	emplace_hint	emplace_hint
insert	insert	insert	insert	insert	insert	insert	insert	insert
erase	erase	erase	erase	erase	erase	erase	erase	erase
clear	clear	clear	clear	clear	clear	clear	clear	clear
swap	swap	swap	swap	swap	swap	swap	swap	swap
operations	count	count	count	count	count	count	count	count	count
find	find	find	find	find	find	find	find	find
equal_range	equal_range	equal_range	equal_range	equal_range	equal_range	equal_range	equal_range	equal_range
lower_bound	lower_bound	lower_bound	lower_bound	lower_bound
upper_bound	upper_bound	upper_bound	upper_bound	upper_bound
observers	get_allocator	get_allocator	get_allocator	get_allocator	get_allocator	get_allocator	get_allocator	get_allocator	get_allocator
key_comp	key_comp	key_comp	key_comp	key_comp
value_comp	value_comp	value_comp	value_comp	value_comp
key_eq					key_eq	key_eq	key_eq	key_eq
hash_function					hash_function	hash_function	hash_function	hash_function
buckets	bucket					bucket	bucket	bucket	bucket
bucket_count					bucket_count	bucket_count	bucket_count	bucket_count
bucket_size					bucket_size	bucket_size	bucket_size	bucket_size
max_bucket_count					max_bucket_count	max_bucket_count	max_bucket_count	max_bucket_count
hash policy	rehash					rehash	rehash	rehash	rehash
load_factor					load_factor	load_factor	load_factor	load_factor
max_load_factor					max_load_factor	max_load_factor	max_load_factor	max_load_factor