The STL queue
is a container adapter that represents a first-in, first-out (FIFO) queue. Only the oldest inserted element in the queue
can be accessed.
queue
is a container adapter, not a true STL container, and is implemented in terms of another linear container class like list
or deque
. To explicitly specify which container to use in the queue
, parametrize the queue as queue<T, ContainerType<T> >
. Note that you cannot build a queue
around a vector
, since vector
does not have a pop_front
member function.
Enqueues a new element into the queue.
Dequeues the first element of the queue
. The behavior is undefined if the queue
has no elements, so be sure not to pop off of an empty queue
. Note that pop
does not return a value; use front
to get the value before pop
ping.
Returns the first element of the queue
(the one that will be removed by pop
). The behavior is undefined if the queue
has no elements, so be sure not to access the front element of an empty queue
. The front
function returns a reference to the front element of the queue
, and you can modify the element if you so choose.
Returns the number of elements stored in the queue
.
Returns whether the queue
is empty. It's considered good practice to call empty
to determine whether the queue
is empty rather than checking whether size()
returns zero.
queue
around an existing container.Constructs a new queue
whose contents are equal to those of the specified container. This constructor is rarely used, but is useful if you already have the data you want to use in the queue
.
Returns the last element of the queue
(the one most recently added). The behavior is undefined if the queue
has no elements, so be sure not to access the back element of an empty queue
. The back
function returns a reference to the back element of the queue
, and you can modify the element if you so choose.