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Introduction to queue
Queue is a data structure designed to operate in FIFO (First in First out) context. In queue elements are inserted from rear end and get removed from front end.
Queue class is container adapter. Container is an objects that hold data of same type. Queue can be created from different sequence containers. Container adapters do not support iterators therefore we cannot use them for data manipulation. However they support push() and pop() member functions for data insertion and deletion respectively.
Definition
Below is definition of std::queuer from <queue> header file
template <class T, class Container = deque<T> > class queue;
Parameters
-
T − Type of the element contained.
T may be substituted by any other data type including user-defined type.
-
Container − Type of the underlying container object.
Member types
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 | container_type | Second parameter of the template |
| 3 | size_type | size_t |
| 4 | reference | value_type& |
| 5 | const_reference | const value_type& |
| 6 | difference_type | ptrdiff_t |
Functions from <queue>
Below is list of all methods from <queue> header.
Constructors
| Sr.No. | Method & Description |
|---|---|
| 1 | queue::queue
Constructs an empty queue object, with zero elements. |
Destructor
| Sr.No. | Method & Description |
|---|---|
| 1 | queue::~queue
Destroys queue by deallocating container memory. |
Member functions
| Sr.No. | Method & Description |
|---|---|
| 1 | queue::back
Returns a reference to the last element of queue. |
| 2 | queue::emplace
Constructs and inserts new element at the end of queue. |
| 3 | queue::empty
Tests whether queue is empty or not. |
| 4 | queue::front
Returns a reference to the first element of the queue. |
| 5 | queue::operator=
Assigns new contents to the queue by replacing old ones. |
| 6 | queue::pop
Removes front element of the queue. |
| 7 | queue::push
Inserts new element at the end of queue. |
| 8 | queue::size
Returns the total number of elements present in the queue. |
| 9 | queue::swap
Exchanges the contents of queue with contents of another queue. |
Non-member overloaded functions
| Sr.No. | Method & Description |
|---|---|
| 1 | operator==
Tests whether two queues are equal or not. |
| 2 | operator!=
Tests whether two queues are equal or not. |
| 3 | operator<
Tests whether first queue is less than other or not. |
| 4 | operator<=
Tests whether first queue is less than or equal to other or not. |
| 5 | operator>
Tests whether first queue is greater than other or not. |
| 6 | operator>=
Tests whether first queue is greater than or equal to other or not. |
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