Questions
16 of 17
1What is the average and worst-case time complexity for lookup in a Hash Table?
2What is a Hash Collision?
3What is the difference between HashMap, TreeMap, and LinkedHashMap?
4Why is the worst-case lookup O(n)? How do modern implementations avoid this? (Tree buckets)
5What are the security implications of Hash Collision attacks (HashDoS)?
6What is the Load Factor? How does it trigger a Rehash/Resize?
7What is a Bloom Filter? When is it used? (Cache penetration, Spell check)
8What is a Hash Table? What is a Key-Value pair?
9What is a Cryptographic Hash? How does it differ from a regular hash?
10How do you design a Hash Table from scratch?
11What is a Hash Function? What makes a good hash function?
12What is the significance of Equals() and GetHashCode() in C#/Java when using objects as keys?
13What is Consistent Hashing? How is it used in Distributed Systems?
14Explain Separate Chaining. (Buckets/Linked Lists)
15Explain Open Addressing. (Linear Probing, Quadratic Probing, Double Hashing)
16Why can't we use a Hash Table efficiently for Ordered operations (e.g., find min/max)?
17Why is it bad to use a mutable object as a key in a HashMap?
Data-StructuresData-Structures
Basics
Complexity Analysis
Arrays and Strings
Linked Lists
Stacks and Queues
Hash Tables
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Why can't we use a Hash Table efficiently for Ordered operations (e.g., find min/max)?

Hash Tables and Ordered Operations

javascript
  1. 1

    Equality lookup is expected O(1).

  2. 2

    Finding min/max generally requires scanning all keys: O(n).

  3. 3

    Sorted iteration requires sorting keys, typically O(n log n).

  4. 4

    A balanced search tree provides ordered operations in O(log n).

  5. 5

    A specialized ordered data structure should be chosen when range queries or ordering are first-class requirements.

Difficulty: 2/10

Follow-up Questions

  • ❓When would you choose TreeMap over HashMap?
  • ❓How would you support efficient range queries?