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.
DefinitionBelow 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.
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 constructorConstructs an empty container, with zero elements.
2 vector::vector fill constructorConstructs a container with n elements and assignd val to each element.
3 vector::vector range constructorConstructs a container with as many elements in range of first to last.
4 vector::vector copy constructorConstructs a container with copy of each elements present in existing container x.
5 vector::vector move constructorConstructs the container with the contents of other using move semantics.
6 vector::vector initializer list constructorConstructs a container from initializer list.
Destructor Sr.No. Method & Description 1 vector::~vectorDestroys container by deallocating container memory.
Member functions Sr.No. Method & Description 1 vector::assign fill versionAssign new values to the vector elements by replacing old ones.
2 vector::assign range versionAssign new values to the vector elements by replacing old ones.
3 vector::assign initializer list versionAssign new values to the vector elements by replacing old ones.
4 vector::atReturns reference to the element present at location n in the vector.
5 vector::backReturns a reference to the last element of the vector.
6 vector::beginReturn a random access iterator pointing to the first element of the vector.
7 vector::capacityReturns the size of allocate storage, expressed in terms of elements.
8 vector::cbeginReturns a constant random access iterator which points to the beginning of the vector.
9 vector::cendReturns a constant random access iterator which points to the beginning of the vector.
10 vector::clearDestroys the vector by removing all elements from the vector and sets size of vector to zero.
11 vector::crbeginReturns a constant reverse iterator which points to the reverser beginning of the container.
12 vector::crendReturns a constant reverse iterator which points to the reverse end of the vector.
13 vector::dataReturns a pointer to the first element of the vector container.
14 vector::emplaceExtends container by inserting new element at position.
15 vector::emplace_backInserts new element at the end of vector.
16 vector::emptyTests whether vector is empty or not.
17 vector::endReturns an iterator which points to past-the-end element in the vector container.
18 vector::erase position versionRemoves single element from the the vector.
19 vector::erase range versionRemoves single element from the the vector.
20 vector::frontReturns a reference to the first element of the vector.
21 vector::get_allocatorReturns an allocator associated with vector.
22 vector::insert single element versionExtends iterator by inserting new element at position.
23 vector::insert fill versionExtends vector by inserting new element in the container.
24 vector::insert range versionExtends vector by inserting new element in the container.
25 vector::insert move versionExtends vector by inserting new element in the container.
26 vector::insert initializer list versionExtends vector by inserting new element in the container.
27 vector::max_sizeReturns the maximum number of elements can be held by vector.
28 vector::operator= copy versionAssign new contents to the vector by replacing old ones and modifies size if necessary.
29 vector::operator= move versionAssign new contents to the vector by replacing old ones and modifies size if necessary.
30 vector::operator = initializer list versionAssign 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_backRemoves last element from vector and reduces size of vector by one.
33 vector::push_backInserts new element at the end of vector and increases size of vector by one.
34 vector::rbeginReturns a reverse iterator which points to the last element of the vector.
35 vector::rendReturns a reverse iterator which points to the reverse end of the vector.
36 vector::reserveRequests to reserve vector capacity be at least enough to contain n elements.
37 vector::resizeChanges the size of vector.
38 vector::shrink_to_fitRequests the container to reduce it's capacity to fit its size.
39 vector::sizeReturns the number of elements present in the vector.
40 vector::swapExchanges 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 swapExchanges the contents of two vector.
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