HackerRank Queue Quiz-1

A queue is an abstract data structure that contains a collection of elements. Queue implements the FIFO mechanism i.e. the element that is inserted first is also deleted first. 

 

Queues in the application areas are implied as the container adaptors

Different types of Queues are circular queue, priority queue, doubly ended queue

We need two queues to implement a stack.

1. First queue to which we enqueue elements


2. Second queue from which we dequeue elements

 the Priority queue of pairs can have two types of ordering –

• Ordered by the first element of pair


• Ordered by the second element of pair

All of the above algorithms are implemented using queues

 

Circular queue is used when we want the iterator to comeback to start when we reach the last element of the queue. So there is no end iterator for the circular queue. There is no readily available data structure in C++ for circular queues.

 

• enqueue - adds an item to the end of the queue


• dequeue - remove an item from front of the queue


• initialize - create an empty queue


• isEmpty - tests for whether or not queue is empty


• isFull - tests to see if queue is full (not needed if data structure grows automatically)


• front - looks at value of the first item but do not remove it

Priority Queue is an extension of the queue with following properties.

1. Every item has a priority associated with it.


2. An element with high priority is dequeued before an element with low priority.


3. If two elements have the same priority, they are served according to their order in the queue.

There are two containers in the Standard C++ Library that can be used to construct priority queues: vectors or deques. By default, a priority_queue will use a vector.