What are the advantages and disadvantages of the hash table data structure?

A hash table is a data structure that stores key-value pairs and provides fast access to data.

Advantages:

• Fast access to elements — average search, insertion, and deletion time around O(1).
• Efficient for implementing dictionaries, caches, and indexes.

Disadvantages:

• Collisions can occur when different keys have the same hash — additional methods (chaining, open addressing) are needed to resolve them.
• Memory may be used inefficiently due to the need to allocate an array with some spare capacity.
• Does not guarantee the order of elements.
• Performance depends on the quality of the hash function.

In C/C++, std::unordered_map is often used for hash tables, which implements these principles.