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Advanced Topic 47 of 52 Data Structures

Cuckoo Hashing

Hashing scheme with two tables guaranteeing constant lookup.

How it works

Each key can live in one of two positions from two hash functions; inserting kicks out the current occupant to its alternative home, repeating until placed. Lookups check at most two slots: worst-case O(1).

Where it is used

Hardware routers, high-performance tables.

Common pitfall

Insert cycles force a rehash; load factor must stay below about 50% for two tables.

Where it fits in the course

Cuckoo Hashing is topic 47 of 52 in Data Structures, rated Advanced. It follows Van Emde Boas Trees. The next topic is Count-Min Sketch.

Practice and explore

How to study this topic

  1. Read the explanation above and restate the definition in your own words.
  2. Open the interactive lesson and answer its mini quiz.
  3. Read the common pitfall, then write a short example that avoids it.
  4. Check your understanding in the Data Structures quiz, and revisit the topic if you miss a question.

Frequently asked questions

What is Cuckoo Hashing?
Hashing scheme with two tables guaranteeing constant lookup. It belongs to Data Structures and is an advanced-level topic.
Where do people use Cuckoo Hashing?
Hardware routers, high-performance tables.
What is the most common mistake with Cuckoo Hashing?
Insert cycles force a rehash; load factor must stay below about 50% for two tables.
What should I learn before this topic?
Start with Van Emde Boas Trees, the topic just before it in Data Structures.
How can I practice it?
Answer the mini quiz in the interactive lesson, then take the Data Structures quiz. You can also explore Hash Table in the Visual Lab.
Is Cuckoo Hashing hard to learn?
It is an Advanced topic. Expect to read the explanation more than once and to connect it with earlier topics. Working through a small example by hand helps most.
How long does it take to learn Cuckoo Hashing?
Most learners can read the explanation and finish the interactive lesson in under an hour. Fluency comes from applying the idea, so plan a few short practice sessions with the quiz.
Which topics are related to Cuckoo Hashing?
Van Emde Boas Trees, Count-Min Sketch, Fibonacci Heaps are closely connected. The full list is in the related topics section of this page.
What should I study after Cuckoo Hashing?
Continue with Count-Min Sketch, the next topic in Data Structures.

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