Programming Concepts Intermediate

What is Hash Table?

A data structure that maps keys to values using a hash function, providing average O(1) time complexity for lookups, insertions, and deletions.

Hash tables compute a hash of the key to determine where to store the value in an array. Collisions (different keys mapping to same index) are handled by chaining (linked lists) or open addressing (probing nearby slots).

Hash tables power dictionaries (Python dict), objects (JavaScript), HashMaps (Java), and associative arrays (PHP). They are the most commonly used data structure for fast key-based lookups. Performance degrades with many collisions or high load factors.

Learn More About This Topic

Related reading

Java Programming for Complete Beginners

Related reading

JavaScript ES6+ Modern Features

Related reading

Related Terms

The process of finding and fixing errors (bugs) in software code to ensure correct program behavior.

The implied cost of additional rework caused by choosing a quick solution now instead of a better approach that would take longer.

A mathematical notation that describes the worst-case performance of an algorithm as input size grows.

A surface indication in code that usually corresponds to a deeper problem in the system, suggesting the need for refactoring.

Testing individual components or functions of a program in isolation to verify they work correctly.

A software development methodology that emphasizes iterative development, collaboration, and rapid response to change.

View All Programming Concepts Terms →