Types of queues

The queue from the last lesson is the plain kind. You'll meet four kinds in total. They differ in two things: where items may join and leave, and who gets served next.

Four kinds of queue. A simple queue joins at the back and leaves at the front. A circular queue is the same on a fixed ring of slots. A deque joins and leaves at both ends. A priority queue always serves the smallest (or largest) key first.

1. Simple queue

Join at the back, leave from the front, first in, first out — exactly the queue from the last lesson. It's the one you want for fairness and order: print jobs, requests to a server, messages between programs, and the frontier of a breadth-first search.

Free account

Keep reading. It's free.

Sign up to read the rest of this lesson: 5 more sections, 3 drawings, a dry-run simulator and code in JavaScript, Python, Java and C++.

Still to come

2. Circular queue (ring buffer)
3. Deque (double-ended queue)
4. Priority queue
Which built-in is which?
Key takeaways

Prev Next

Mark completed

Was this helpful?

StackLast-in, first-out — the structure behind call stacks, undo history, and expression parsing.6 lessons · 13 problems
Binary TreeHierarchical structures for representing nested relationships and enabling fast search.5 lessons · 16 problems
Linked ListNodes linked one direction by pointers instead of contiguous memory.4 lessons · 12 problems

Types of queues

1. Simple queue

Keep reading. It's free.

Keep exploring