Chained Hash Table Implementation

Author: Giannis Loizou
Description: Custom implementation of a chained hash table (linked-list-based collision handling) with dynamic rehashing support.

This project demonstrates the design, implementation, and testing of a hash table data structure, including handling collisions, automatic resizing, and an interactive command-line interface for testing and exploration.

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Features

• Chained Hashing: Handles collisions using linked lists for each bucket.
• Rehashing: Automatically doubles the bucket size when load factor exceeds 2.0.
• CRUD Operations:
  • Insert key-value pairs
  • Retrieve values by key
  • Delete entries
• Interactive Menu: Command-line interface to manage the hash table manually.
• Edge Case Handling: Supports empty hash table operations, duplicate key updates, and None values as data.
• Statistics: Displays table size, number of elements, and load factor.

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Technology & Concepts

• Programming Language: Python 3
• Data Structures: Linked Lists, Hash Tables
• Concepts: Collision handling, dynamic resizing (rehashing), load factor, key-value storage
• Soft Skills Applied: Testing, debugging, user interaction design

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Project Structure

• ChainedHash Class: Core implementation of the hash table.
• Node Class: Internal linked-list node for collision chains.
• Test Driver (Main):
  • Automatic tests for insertion, retrieval, deletion, duplicates, rehashing, and edge cases.
  • Interactive menu for manual testing.

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Usage

1. Clone the repository: git clone https://github.com/Hydrocast/Chained-Hash-Map-Implementation.git

2. cd ChainedHashMap

3. Run the Python script: python3 chained_hash.py

4. Follow the interactive menu to:

• Insert key-value pairs
• Retrieve data
• Delete entries
• Display table structure
• View statistics

Notes:

• Keys must be integers. Values can be strings or None.
• The system also handles rehashing automatically once the load factor exceeds 2.0.

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Testing

• The implementation includes extensive automated testing:
• Insert 20+ elements to trigger rehashing
• Retrieve inserted elements
• Delete elements (including first/last in chains)
• Test duplicate insertion updates
• Edge cases (empty table operations, None values)
• Interactive tests allow manual verification of the hash table's correctness.