Explain Separate Chaining. (Buckets/Linked Lists)

Difficulty: 5/10

collision resolution, hash tables, linked lists

Separate Chaining

Separate chaining resolves collisions by allowing each Hash Table bucket to contain multiple entries. The bucket can be implemented using a linked list, dynamic structure, or, in some modern implementations, a balanced tree when the chain becomes sufficiently large.

javascript

1
Multiple keys can occupy the same bucket.
2
Collision entries are linked or otherwise grouped together.
3
Average lookup remains close to O(1) when the load factor is controlled.
4
Worst-case lookup can become O(n) if many keys fall into one bucket.
5
Separate chaining makes deletion simpler than many open-addressing designs.
6
Modern implementations may treeify heavily populated buckets.

Scenario Questions

0-2 years experience

2-5 years experience

1We have a service that uses a hash table with separate chaining, and after a traffic spike we notice lookups are slower. What could be causing the slowdown and how would you investigate?

Follow-up Questions