Circular Linked Lists

The Ring With No End

1:00

How a linked list becomes a ring by making the tail point back to the head — and why that one change powers round-robin scheduling, ring buffers, and O(1) inserts at both ends.

By the end, you can

Explain why `tail.next` is the head in a circular linked list and why no node has a `null` next pointer.
Wire the tail back to the head to convert a linear list into a ring.
Trace a single traversal lap using the pointer-equality stop condition.
Identify why `while (cur != null)` causes an infinite loop on a circular list and name two safe alternatives.
Describe how a tail pointer achieves O(1) inserts at both the front and back.
Enumerate real-world use cases (round-robin scheduling, ring buffers, looping playlists) and explain why the circular structure suits them.
Distinguish singly circular from doubly circular linked lists in terms of structure and capability.

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