What is a hash table and what problems can it have?

A hash table is a data structure that stores key-value pairs and provides fast access to data by key, usually in near O(1) time.

How it works: a key is transformed using a hash function into an array index where the value is stored.

Problems that may arise:

• Collisions: when different keys have the same hash, they need to be handled (chaining, open addressing).
• Uneven distribution: a poor hash function can lead to clustering of elements in certain buckets, degrading performance.
• Resizing: as the number of elements grows, the table needs to be expanded and data redistributed, which requires resources.
• Memory: hash tables can occupy more memory due to the need to store additional structures for collisions.

In Go, the built-in map is implemented as a hash table with thoughtful collision handling and dynamic resizing.