STL Containers

Standard Template Library: Containers

A container is a holder object that stores a collection 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 class independently of the underlying container class used.

Container class templates

Sequence containers:

vector

Vector (class template)

deque

Double ended queue (class template)

list	List (class template)

Container adaptors:

stack

LIFO stack (class template)

queue

FIFO queue (class template)

priority_queue

Priority queue (class template)

Associative containers:

set	Set (class template)

multiset

Multiple-key set (class template)

map	Map (class template)

multimap

Multiple-key map (class template)

bitset

Bitset (class template)

Member map

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

			Sequence containers			Associative containers
Headers
Members		complex	vector	deque	list	set	multiset	map	multimap	bitset
	constructor	*	constructor	constructor	constructor	constructor	constructor	constructor	constructor	constructor
	destructor	O(n)	destructor	destructor	destructor	destructor	destructor	destructor	destructor
	operator=	O(n)	operator=	operator=	operator=	operator=	operator=	operator=	operator=	operators
iterators	begin	O(1)	begin	begin	begin	begin	begin	begin	begin
	end	O(1)	end	end	end	end	end	end	end
	rbegin	O(1)	rbegin	rbegin	rbegin	rbegin	rbegin	rbegin	rbegin
	rend	O(1)	rend	rend	rend	rend	rend	rend	rend
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
	empty	O(1)	empty	empty	empty	empty	empty	empty	empty
	resize	O(n)	resize	resize	resize
element access	front	O(1)	front	front	front
	back	O(1)	back	back	back
	operator[]	*	operator[]	operator[]				operator[]		operator[]
	at	O(1)	at	at
modifiers	assign	O(n)	assign	assign	assign
	insert	*	insert	insert	insert	insert	insert	insert	insert
	erase	*	erase	erase	erase	erase	erase	erase	erase
	swap	O(1)	swap	swap	swap	swap	swap	swap	swap
	clear	O(n)	clear	clear	clear	clear	clear	clear	clear
	push_front	O(1)		push_front	push_front
	pop_front	O(1)		pop_front	pop_front
	push_back	O(1)	push_back	push_back	push_back
	pop_back	O(1)	pop_back	pop_back	pop_back
observers	key_comp	O(1)				key_comp	key_comp	key_comp	key_comp
	value_comp	O(1)				value_comp	value_comp	value_comp	value_comp
operations	find	O(log n)				find	find	find	find
	count	O(log n)				count	count	count	count	count
	lower_bound	O(log n)				lower_bound	lower_bound	lower_bound	lower_bound
	upper_bound	O(log n)				upper_bound	upper_bound	upper_bound	upper_bound
	equal_range	O(log n)				equal_range	equal_range	equal_range	equal_range
unique members			capacity reserve		splice remove remove_if unique merge sort reverse					set reset flip to_ulong to_string test any none

Amortized complexity shown. Legend: O(1) constant <>Container adaptors:

			Container Adaptors
Headers
Members			stack	queue	priority_queue
	constructor	*	constructor	constructor	constructor
capacity	size	O(1)	size	size	size
	empty	O(1)	empty	empty	empty
element access	front	O(1)		front
	back	O(1)		back
	top	O(1)	top		top
modifiers	push	O(1)	push	push	push
	pop	O(1)	pop	pop	pop