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Implement a hash table with put/get | Paradromics Interview Question

Q: Implement a hash table with put/get

This question evaluates implementation and design skills for hash-based data structures, testing competency in data structures, hashing, collision handling, and achieving expected O(1) put/get performance in the Coding & Algorithms domain.

Problem

Implement a simplified hash table (hash map) data structure from scratch.

Required API

Design a class HashTable with:

HashTable(int numBuckets) (constructor): initialize internal storage with a fixed number of buckets.
void put(K key, V value) : insert a key/value pair. If the key already exists, overwrite its value.
V get(K key) : return the value for key , or a sentinel (e.g., null / -1 ) if the key is not present.

Note: delete/remove is not required.

Assumptions / Constraints

You may assume keys are non-null.
You must handle hash collisions correctly.
Target average time complexity: O(1) for put and get (amortized/expected).
You may not use a built-in hash map/dictionary.

Follow-up discussion (conceptual)

What makes a hash function “good,” and how does key distribution affect performance?
How does the choice of numBuckets (and the load factor) impact collisions and runtime?
Compare common collision-resolution strategies:
- Separate chaining (buckets)
- Open addressing (e.g., linear/quadratic probing, double hashing)
If using open addressing, describe how probing (“hopping”) works and what pitfalls it introduces (e.g., clustering, tombstones).

Problem

Implement a simplified hash table (hash map) data structure from scratch.

Required API

Design a class HashTable with:

HashTable(int numBuckets) (constructor): initialize internal storage with a fixed number of buckets.

void put(K key, V value) : insert a key/value pair. If the key already exists, overwrite its value.

V get(K key) : return the value for key , or a sentinel (e.g., null / -1 ) if the key is not present.

Note: delete/remove is not required.

Assumptions / Constraints

You may assume keys are non-null.

You must handle hash collisions correctly.

Target average time complexity: O(1) for put and get (amortized/expected).

You may not use a built-in hash map/dictionary.

Follow-up discussion (conceptual)

What makes a hash function “good,” and how does key distribution affect performance?

How does the choice of numBuckets (and the load factor) impact collisions and runtime?

Compare common collision-resolution strategies:

Separate chaining (buckets)
Open addressing (e.g., linear/quadratic probing, double hashing)

If using open addressing, describe how probing (“hopping”) works and what pitfalls it introduces (e.g., clustering, tombstones).

Implement a hash table with put/get

Quick Overview

Problem

Required API

Assumptions / Constraints

Follow-up discussion (conceptual)

Submit Your Answer to Earn 20XP

Implement a hash table with put/get

Quick Overview

Problem

Required API

Assumptions / Constraints

Follow-up discussion (conceptual)

Submit Your Answer to Earn 20XP