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# std::queue::queue

From cppreference.com
< cpp‎ | container‎ | queue

[edit template]

| (1) |
explicit queue( const Container& cont = Container() ); |  | (until C++11)
explicit queue( const Container& cont ); |  | (since C++11)
explicit queue( Container&& cont = Container() ); | (2) | (since C++11)
queue( const queue& other ); | (3) |
queue( queue&& other ); | (4) | (since C++11)
template< class Alloc > explicit queue( const Alloc& alloc ); | (5) | (since C++11)
template< class Alloc > queue( const Container& cont, const Alloc& alloc ); | (6) | (since C++11)
template< class Alloc > queue( Container&& cont, const Alloc& alloc ); | (7) | (since C++11)
template< class Alloc > queue( const queue& other, const Alloc& alloc ); | (8) | (since C++11)
template< class Alloc > queue( queue&& other, const Alloc& alloc ); | (9) | (since C++11)

Constructs new underlying container of the container adaptor from a variety of data sources.

1) Copy-constructs the underlying container `c` with the contents of `cont`. This is also the default constructor (until C++11)
2) Move-constructs the underlying container `c` with std::move(cont). This is also the default constructor (since C++11)
3) Copy constructor. The adaptor is copy-constructed with the contents of other.c. (implicitly declared)
4) Move constructor. The adaptor is constructed with std::move(other.c). (implicitly declared)
5-9) The following constructors are only defined if std::uses_allocator<container_type, Alloc>::value == true, that is, if the underlying container is an allocator-aware container (true for all standard library containers).
5) Constructs the underlying container using `alloc` as allocator, as if by c(alloc).
6) Constructs the underlying container with the contents of `cont` and using `alloc` as allocator, as if by c(cont, alloc).
7) Constructs the underlying container with the contents of `cont` using move semantics while utilising `alloc` as allocator, as if by c(std::move(cont), alloc).
8) Constructs the adaptor with the contents of `other.c` and using `alloc` as allocator, as if by c(other.c, alloc).
9) Constructs the adaptor with the contents of `other` using move semantics while utilising `alloc` as allocator, as if by c(std::move(other.c), alloc).

### [edit] Parameters

alloc | - | allocator to use for all memory allocations of the underlying container
other | - | another container adaptor to be used as source to initialize the underlying container
cont | - | container to be used as source to initialize the underlying container
first, last | - | range of elements to initialize with
Type requirements
- `Alloc` must meet the requirements of `Allocator`.
- `Container` must meet the requirements of `Container`. The constructors (5-10) are only defined if `Container` meets the requirements of `AllocatorAwareContainer`
- `InputIt` must meet the requirements of `InputIterator`.

### [edit] Complexity

1, 3, 5, 6, 8: linear in `cont` or `other`

2, 4, 7, 9: constant

| This section is incomplete

### [edit] Example

Run this code

    #include <queue>
    #include <deque>
    #include <iostream>

    int main()
    {
        std::queue<int> c1;
        c1.push(5);
        std::cout << c1.size() << '\n';

        std::queue<int> c2(c1);
        std::cout << c2.size() << '\n';

        std::deque<int> deq {3, 1, 4, 1, 5};
        std::queue<int> c3(deq);
        std::cout << c3.size() << '\n';
    }

Output:

    1
    1
    5

### [edit] See also

operator= | assigns values to the container adaptor (public member function) [edit]

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