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📅  最后修改于: 2020-12-15 04:37:15             🧑  作者: Mango

介绍

向量是可以更改大小的序列容器。容器是保存相同类型数据的对象。顺序容器严格按线性顺序存储元素。

Vector将元素存储在连续的内存位置，并允许使用下标运算符[]直接访问任何元素。与数组不同，向量可以在运行时根据需要缩小或扩展。向量的存储将自动处理。

为了在运行时支持收缩和扩展功能，矢量容器可能会分配一些额外的存储空间以适应可能的增长，因此容器的实际容量大于该大小。因此，与阵列相比，向量消耗更多内存以换取以有效方式管理存储和动态增长的能力。

零尺寸向量也是有效的。在这种情况下，vector.begin()和vector.end()指向相同的位置。但是调用front()或back()的行为是不确定的。

定义

下面是头文件中std :: vector的定义

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

参量

  • T-所包含元素的类型。

    T可以用任何其他数据类型(包括用户定义的类型)代替。

  • Alloc-分配器对象的类型。

    默认情况下，使用分配器类模板，该模板定义了最简单的内存分配模型并且与值无关。

会员类型

成员函数可以将以下成员类型用作参数或返回类型。

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
10 const_reverse_iterator std::reverse_iterator
11 size_type size_t
12 difference_type ptrdiff_t

中的函数

以下是标头中所有方法的列表。

建设者

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.

析构函数

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

Destroys container by deallocating container memory.

会员职能

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.

非成员重载函数

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.