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    std::vector<T,Allocator>::vector

    From cppreference.com
     
    C++
     
    Containers library
     
    std::vector
    Member types
    Member functions
    Non-member functions
    (until C++20)(until C++20)(until C++20)(until C++20)(until C++20)
    Deduction guides(C++17)
     
    (1)
    vector() : vector(Allocator()) {}
    		 (since C++11)
    (until C++17)
    vector() noexcept(noexcept(Allocator())) : vector(Allocator()) {}
    		 (since C++17)
    (constexpr since C++20)
    (2)
    explicit vector( const Allocator& alloc = Allocator() );
    		 (until C++11)
    explicit vector( const Allocator& alloc );
    		 (since C++11)
    (noexcept since C++17)
    (constexpr since C++20)
    explicit vector( size_type count, const Allocator& alloc = Allocator() );
    		 (3) (since C++11)
    (4)
    explicit vector( size_type count, const T& value = T(), const Allocator& alloc = Allocator() );
    		 (until C++11)
    vector( size_type count, const T& value, const Allocator& alloc = Allocator() );
    		 (since C++11)
    (constexpr since C++20)
    template< class InputIt > vector( InputIt first, InputIt last, const Allocator& alloc = Allocator() );
    		 (5) (constexpr since C++20)
    template< container-compatible-range<T> R > constexpr vector( std::from_range_t, R&& rg, const Allocator& alloc = Allocator() );
    		 (6) (since C++23)
    vector( const vector& other );
    		 (7) (constexpr since C++20)
    vector( vector&& other );
    		 (8) (since C++11)
    (noexcept since C++17)
    (constexpr since C++20)
    (9)
    vector( const vector& other, const Allocator& alloc );
    		 (since C++11)
    (constexpr since C++20)
    (until C++23)
    constexpr vector( const vector& other, const std::type_identity_t<Allocator>& alloc );
    		 (since C++23)
    (10)
    vector( vector&& other, const Allocator& alloc );
    		 (since C++11)
    (until C++23)
    constexpr vector( vector&& other, const std::type_identity_t<Allocator>& alloc );
    		 (since C++23)
    vector( std::initializer_list<T> init, const Allocator& alloc = Allocator() );
    		 (11) (since C++11)
    See More

    Constructs a new vector from a variety of data sources, optionally using a user supplied allocator alloc.

    1) The default constructor since C++11. Constructs an empty vector with a default-constructed allocator.
    If Allocator is not DefaultConstructible, the behavior is undefined.
    2) The default constructor until C++11. Constructs an empty vector with the given allocator alloc.
    3) Constructs a vector with count default-inserted objects of T. No copies are made.
    If T is not DefaultInsertable into std::vector<T>, the behavior is undefined.
    4) Constructs a vector with count copies of elements with value value.

    If T is not CopyInsertable into std::vector<T>, the behavior is undefined.

    		(since C++11)
    5) Constructs a vector with the contents of the range [first, last). Each iterator in [first, last) is dereferenced exactly once.

    If InputIt does not satisfy the requirements of LegacyInputIterator, overload (4) is called instead with arguments static_cast<size_type>(first), last and alloc.

    		(until C++11)

    This overload participates in overload resolution only if InputIt satisfies the requirements of LegacyInputIterator.

    If any of the following conditions is satisfied, the behavior is undefined:

    		(since C++11)
    6) Constructs a vector with the contents of the range rg. Each iterator in rg is dereferenced exactly once.
    If any of the following conditions is satisfied, the behavior is undefined:
    7-10) Constructs a vector with the contents of other.
    7) The copy constructor.

    The allocator is obtained as if by calling std::allocator_traits<Allocator>::
    select_on_container_copy_construction
    (other.get_allocator())    .

    		(since C++11)
    8) The move constructor. The allocator is obtained by move construction from other.get_allocator().
    9) Same as the copy constructor, except that alloc is used as the allocator.
    If T is not CopyInsertable into std::vector<T>, the behavior is undefined.
    10) Same as the move constructor, except that alloc is used as the allocator.
    If T is not MoveInsertable into std::vector<T>, the behavior is undefined.
    11) Equivalent to vector(il.begin(), il.end(), alloc).

    Parameters

    alloc - allocator to use for all memory allocations of this container
    count - the size of the container
    value - the value to initialize elements of the container with
    first, last - the pair of iterators defining the range of elements to copy the elements from
    other - another container to be used as source to initialize the elements of the container with
    init - initializer list to initialize the elements of the container with
    rg - a container compatible range

    Complexity

    1,2) Constant.
    3,4) Linear in count.
    5) Given std::distance(first, last) as N:
    • If first and last are both forward, bidirectional or random-access iterators,
    • The copy constructor of T is only called N  times, and
    • No reallocation occurs.
    • Otherwise (first and last are just input iterators),
    • The copy constructor of T is called O(N) times, and
    • Reallocation occurs O(log N) times.
    6) Given ranges::distance(rg) as N:
    • If R models ranges::forward_range or ranges::sized_range,
    • Initializes exactly N elements from the result of dereferencing successive iterators of rg, and
    • No reallocation occurs.
    • Otherwise (R models input range),
    • The copy or move constructor of T is called O(N) times, and
    • Reallocation occurs O(log N) times.
    7) Linear in other.size().
    8) Constant.
    9) Linear in other.size().
    10) Linear in other.size() if alloc != other.get_allocator(), otherwise constant.
    11) Linear in init.size().

    Exceptions

    Calls to Allocator::allocate may throw.

    Notes

    After container move construction (overload (8)), references, pointers, and iterators (other than the end iterator) to other remain valid, but refer to elements that are now in *this. The current standard makes this guarantee via the blanket statement in [container.reqmts]/67, and a more direct guarantee is under consideration via LWG issue 2321.

    Feature-test macro Value Std Feature
    __cpp_lib_containers_ranges 202202L (C++23) Ranges-aware construction and insertion; overload (6)

    Example

    Run this code
    #include <iostream>
#include <string>
#include <vector>

template<typename T>
std::ostream& operator<<(std::ostream& s, const std::vector<T>& v)
{
    s.put('{');
    for (char comma[]{'\0', ' ', '\0'}; const auto& e : v)
        s << comma << e, comma[0] = ',';
    return s << "}\n";
}

int main()
{
    // C++11 initializer list syntax:
    std::vector<std::string> words1{"the", "frogurt", "is", "also", "cursed"};
    std::cout << "1: " << words1;
    
    // words2 == words1
    std::vector<std::string> words2(words1.begin(), words1.end());
    std::cout << "2: " << words2;
    
    // words3 == words1
    std::vector<std::string> words3(words1);
    std::cout << "3: " << words3;
    
    // words4 is {"Mo", "Mo", "Mo", "Mo", "Mo"}
    std::vector<std::string> words4(5, "Mo");
    std::cout << "4: " << words4;
    
    const auto rg = {"cat", "cow", "crow"};
#ifdef __cpp_lib_containers_ranges
    std::vector<std::string> words5(std::from_range, rg); // overload (6)
#else
    std::vector<std::string> words5(rg.begin(), rg.end()); // overload (5)
#endif
    std::cout << "5: " << words5;
}

    Output: 

    1: {the, frogurt, is, also, cursed}
2: {the, frogurt, is, also, cursed}
3: {the, frogurt, is, also, cursed}
4: {Mo, Mo, Mo, Mo, Mo}
5: {cat, cow, crow}

    Defect reports

    The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

    DR Applied to Behavior as published Correct behavior
    LWG 134 C++98 overload (5) allowed up to 2N  copy
    constructor calls in the input iterator case     		changed to O(N) calls
    LWG 438 C++98 overload (5) would only call overload (4)
    if InputIt is an integral type     		calls overload (4) if InputIt
    is not an LegacyInputIterator
    LWG 2193 C++11 the default constructor was explicit made non-explicit
    LWG 2210 C++11 overload (3) did not have an allocator parameter added the parameter
    N3346 C++11 for overload (3), the elements in
    the container were value-initialized     		they are default-inserted

    See also

    		 assigns values to the container
    (public member function) [edit]
    		assigns values to the container
    (public member function) [edit]