§ 02 — Discrete Structures and Algorithms

Queue Data Structure

Module 6: Queue Data Structure

A queue is a linear structure that follows First-In, First-Out (FIFO) order. The first item added is the first item removed.

A queue uses two ends:

End	Purpose
Rear	New items are inserted here.
Front	Items are removed here.

A real-world example is a line of people waiting for service. The person who arrives first is served first.

Operation	Description
`enqueue`	Adds an item to the rear of the queue.
`dequeue`	Removes an item from the front of the queue.
`peek`	Views the front item without removing it.
`isEmpty`	Checks if the queue has no items.

Method	Description
`add(e)`	Inserts an element and may throw an exception if insertion fails.
`offer(e)`	Inserts an element and returns whether insertion succeeded.
`element()`	Returns the front item but may throw an exception if empty.
`peek()`	Returns the front item or `null` if empty.
`remove()`	Removes and returns the front item; may throw an exception if empty.
`poll()`	Removes and returns the front item or `null` if empty.

Queues may be implemented using arrays, linked lists, pointers, or built-in collection classes.

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