What is an XOR Linked List? Why is it rarely used?
XOR Linked List
An XOR Linked List is a specialized doubly linked list where each node stores the XOR of the addresses of its previous and next nodes instead of storing two separate references. Given one neighboring address and the stored XOR value, the other address can theoretically be reconstructed.
- 1
It can reduce the memory used for two link fields to one XOR field.
- 2
It requires pointer/address arithmetic that is unsafe or unavailable in many managed languages.
- 3
It complicates debugging and memory management.
- 4
Garbage collectors generally do not work naturally with XOR-encoded references.
- 5
It can be difficult to reason about, maintain, and integrate with modern runtimes.
- 6
The small memory saving rarely justifies the complexity in modern application software.
Follow-up Questions
- Why does XOR allow reconstruction of the neighboring address?
- Why is this unsuitable for Java?
- What are safer alternatives for reducing node overhead?