Previous Topic
prerequisite
0.88
Arrays provide constant-time indexed access and contiguous storage that hash tables rely on for bucket addressing, load factor management, and rehashing.
chaining structure
0.82
Singly linked lists act as the per-bucket container for collided keys, allowing O(1) insertions at the head and linear-time scans within a bucket.
data_structure
0.7
Stacks and queues introduce fundamental concepts of data organization and manipulation, which are essential for understanding more complex data structures like hash tables.

Hash Tables

data structures algorithms programming computer science
Hash tables are a data structure that provide fast insertion, deletion, and lookup capabilities. They are widely used in computer science for implementing associative arrays and managing large datasets efficiently.

Introduction to Hash Tables

Hash tables are a fundamental data structure that allow you to store key-value pairs and quickly retrieve the value associated with a given key. They are designed to provide average-case constant time complexity (O(1)) for search, insertion, and deletion operations, making them a preferred choice for many applications.

How Hash Tables Work

A hash table uses a hash function to compute an index into an array of buckets or slots, from which the desired value can be found. The hash function takes a key and converts it into an integer hash code, which is then used to find the appropriate index.

Handling Collisions

One of the challenges with hash tables is handling collisions, which occur when two keys hash to the same index. Common collision resolution techniques include:

  • Chaining: Using a linked list to store all elements that hash to the same index.
  • Open Addressing: Finding another open slot within the hash table when a collision occurs.

Applications of Hash Tables

Hash tables are widely used in various applications, including:

  • Implementing associative arrays and dictionaries.
  • Database indexing.
  • Caching and memoization.
  • Counting the frequencies of items.
Context from Referenced By
Stacks And Queues

Stacks and queues provide foundational knowledge about data storage and retrieval mechanisms that can aid in understanding hash table operations, especially in handling collisions using techniques like chaining.

Context from Related Topics
Databases

In databases, hash tables are used to create efficient indexing systems that drastically improve query performance by reducing the time complexity of data searches.

Pop Quiz
Topic: hash_tables
Level:
True or False:

Hash tables provide average-case constant time complexity for search, insertion, and deletion operations.

Topic: hash_tables
Level:
True or False:

Hash tables use a hash function to map keys to indices in an array.

Next Topic
associated_with
0.85

Big O Notation
Big O notation is used to describe the efficiency of operations on hash tables, such as average-case constant time complexity for insertion, deletion, and lookup.
component_of
0.85

Databases
Hash tables are a fundamental component used in databases for efficient data retrieval and management.
related_to
0.75

Efficient Data Structures
Hash tables are one example of efficient data structures used to manage large datasets, similar to trees and binary search trees, which are also fundamental in computer science.