C++ Library - <vector>


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Introduction

Vectors are sequence container that can change size. Container is a objects that hold data of same type. Sequence containers store elements strictly in linear sequence.

Vector stores elements in contiguous memory locations and enables direct access to any element using subscript operator []. Unlike array, vector can shrink or expand as needed at run time. The storage of the vector is handled automatically.

To support shrink and expand functionality at runtime, vector container may allocate some extra storage to accommodate for possible growth thus container have actual capacity greater than the size. Therefore, compared to array, vector consumes more memory in exchange for the ability to manage storage and grow dynamically in an efficient way.

Zero sized vectors are also valid. In that case vector.begin() and vector.end() points to same location. But behavior of calling front() or back() is undefined.

Definition

Below is definition of std::vector from <vector> header file

template < class T, class Alloc = allocator<T> > class vector;

Parameters

  • T − Type of the element contained.

    T may be substituted by any other data type including user-defined type.

  • Alloc − Type of allocator object.

    By default, the allocator class template is used, which defines the simplest memory allocation model and is value-independent.

Member types

Following member types can be used as parameters or return type by member functions.

Sr.No. Member types Definition
1 value_type T (First parameter of the template)
2 allocator_type Alloc (Second parameter of the template)
3 reference value_type&
4 const_reference const value_type&
5 pointer value_type*
6 const_pointer const value_type*
7 iterator a random access iterator to value_type
8 const_iterator a random access iterator to const value_type
9 reverse_iterator std::reverse_iterator <iterator>
10 const_reverse_iterator std::reverse_iterator <const_iterator>
11 size_type size_t
12 difference_type ptrdiff_t

Functions from <vector>

Below is list of all methods from <vector> header.

Constructors

Sr.No. Method & Description
1 vector::vector default constructor

Constructs an empty container, with zero elements.

2 vector::vector fill constructor

Constructs a container with n elements and assignd val to each element.

3 vector::vector range constructor

Constructs a container with as many elements in range of first to last.

4 vector::vector copy constructor

Constructs a container with copy of each elements present in existing container x.

5 vector::vector move constructor

Constructs the container with the contents of other using move semantics.

6 vector::vector initializer list constructor

Constructs a container from initializer list.

Destructor

Sr.No. Method & Description
1 vector::~vector

Destroys container by deallocating container memory.

Member functions

Sr.No. Method & Description
1 vector::assign fill version

Assign new values to the vector elements by replacing old ones.

2 vector::assign range version

Assign new values to the vector elements by replacing old ones.

3 vector::assign initializer list version

Assign new values to the vector elements by replacing old ones.

4 vector::at

Returns reference to the element present at location n in the vector.

5 vector::back

Returns a reference to the last element of the vector.

6 vector::begin

Return a random access iterator pointing to the first element of the vector.

7 vector::capacity

Returns the size of allocate storage, expressed in terms of elements.

8 vector::cbegin

Returns a constant random access iterator which points to the beginning of the vector.

9 vector::cend

Returns a constant random access iterator which points to the beginning of the vector.

10 vector::clear

Destroys the vector by removing all elements from the vector and sets size of vector to zero.

11 vector::crbegin

Returns a constant reverse iterator which points to the reverser beginning of the container.

12 vector::crend

Returns a constant reverse iterator which points to the reverse end of the vector.

13 vector::data

Returns a pointer to the first element of the vector container.

14 vector::emplace

Extends container by inserting new element at position.

15 vector::emplace_back

Inserts new element at the end of vector.

16 vector::empty

Tests whether vector is empty or not.

17 vector::end

Returns an iterator which points to past-the-end element in the vector container.

18 vector::erase position version

Removes single element from the the vector.

19 vector::erase range version

Removes single element from the the vector.

20 vector::front

Returns a reference to the first element of the vector.

21 vector::get_allocator

Returns an allocator associated with vector.

22 vector::insert single element version

Extends iterator by inserting new element at position.

23 vector::insert fill version

Extends vector by inserting new element in the container.

24 vector::insert range version

Extends vector by inserting new element in the container.

25 vector::insert move version

Extends vector by inserting new element in the container.

26 vector::insert initializer list version

Extends vector by inserting new element in the container.

27 vector::max_size

Returns the maximum number of elements can be held by vector.

28 vector::operator= copy version

Assign new contents to the vector by replacing old ones and modifies size if necessary.

29 vector::operator= move version

Assign new contents to the vector by replacing old ones and modifies size if necessary.

30 vector::operator = initializer list version

Assign new contents to the vector by replacing old ones and modifies size if necessary.

31 vector::operator[]

Returns a reference to the element present at location n.

32 vector::pop_back

Removes last element from vector and reduces size of vector by one.

33 vector::push_back

Inserts new element at the end of vector and increases size of vector by one.

34 vector::rbegin

Returns a reverse iterator which points to the last element of the vector.

35 vector::rend

Returns a reverse iterator which points to the reverse end of the vector.

36 vector::reserve

Requests to reserve vector capacity be at least enough to contain n elements.

37 vector::resize

Changes the size of vector.

38 vector::shrink_to_fit

Requests the container to reduce it's capacity to fit its size.

39 vector::size

Returns the number of elements present in the vector.

40 vector::swap

Exchanges the content of vector with contents of vector x.

Non-member overloaded functions

Sr.No. Method & Description
1 operator ==

Tests whether two vectors are equal or not.

2 operator !=

Tests whether two vectors are equal or not.

3 operator <

Tests whether first vector is less than other or not.

4 operator <=

Tests whether first vector is less than or equal to other or not.

5 operator >

Tests whether first vector is greater than other or not.

6 operator >=

Tests whether first vector is greater than or equal to other or not.

7 swap

Exchanges the contents of two vector.



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