Interview kitsBlog

Your dream job? Lets Git IT.
Interactive technical interview preparation platform designed for modern developers.

XGitHub

Platform

  • Categories

Resources

  • Blog
  • About the app
  • FAQ
  • Feedback

Legal

  • Privacy Policy
  • Terms of Service

© 2026 LetsGit.IT. All rights reserved.

LetsGit.IT/Categories/Data Structures
Data Structuresmedium

Hash table collisions: what is the difference between separate chaining and open addressing?

Tags
#hash-table#collisions#chaining#open-addressing
Back to categoryPractice quiz

Answer

Separate chaining stores colliding keys in a bucket list (or tree). Open addressing keeps all entries in the table and probes alternative slots (e.g., linear/quadratic probing, double hashing). Chaining is simpler for deletes; open addressing can be more cache-friendly but is sensitive to load factor.

Advanced answer

Deep dive

Expanding on the short answer — what usually matters in practice:

  • Context (tags): hash-table, collisions, chaining, open-addressing
  • Complexity: compare typical operations (average vs worst-case).
  • Invariants: what must always hold for correctness.
  • When the choice is wrong: production symptoms (latency, GC, cache misses).
  • Explain the "why", not just the "what" (intuition + consequences).
  • Trade-offs: what you gain/lose (time, memory, complexity, risk).
  • Edge cases: empty inputs, large inputs, invalid inputs, concurrency.

Examples

A tiny example (an explanation template):

// Example: discuss trade-offs for "hash-table-collisions:-what-is-the-difference-be"
function explain() {
  // Start from the core idea:
  // Separate chaining stores colliding keys in a bucket list (or tree). Open addressing keeps 
}

Common pitfalls

  • Too generic: no concrete trade-offs or examples.
  • Mixing average-case and worst-case (e.g., complexity).
  • Ignoring constraints: memory, concurrency, network/disk costs.

Interview follow-ups

  • When would you choose an alternative and why?
  • What production issues show up and how do you diagnose them?

Related questions

Data Structures
Why can a hash table resize cause latency spikes, and how can you mitigate it?
#hash-table#rehash#latency
Data Structures
Cuckoo hashing: what is it and what trade-off does it make?
#hashing#cuckoo-hashing#hash-table
Data Structures
Hash table load factor — what is it and why does resizing happen?
#hash-table
  • How would you test edge cases?
  • #load-factor
    #rehash
    Data Structures
    How do hash tables handle collisions? (chaining vs open addressing)
    #hash-table#collision#chaining