What structure does a hash table use to store data?

A hash table uses an array with computed indices to store data. This structure is fundamental to how hash tables efficiently organize and retrieve information. In a hash table, a hash function takes a key and computes an index in the underlying array where the data associated with that key should be stored. This allows for average-case constant time complexity, O(1), for insertion, deletion, and look-up operations.

When a key is processed through the hash function, the resulting index determines the position in the array where the associated value is stored. If two keys hash to the same index, a collision occurs and typically a method like chaining (which uses linked lists) or open addressing is employed to resolve the issue. However, the primary structure remains an array where the indices are derived from computing the keys.

In contrast, a tree structure organizes data hierarchically, and while efficient for certain operations, it does not provide the same direct indexing benefits as a hash table. An array of linked lists might represent a collision resolution strategy within a hash table but is not the primary structure used for data organization. A flat file structure involves sequencing data linearly without the efficiency of hashing. Thus, the correct option clearly illustrates the foundational mechanism of how hash tables operate.