BucketArray

BucketArray is a term used in computer science to describe a data structure that organizes elements into a collection of buckets. The structure typically consists of an outer array of buckets, each of which stores items that hash to that bucket or belong to that category. Bucket arrays are used to implement hash-based containers, sparse data structures, and grouped processing of items.

Structure and operations: An index is derived from a key by applying a hash function and taking the modulus with the number of buckets. Each bucket is a container, such as a linked list, a dynamic array, or another small structure. Insertion places the item in the appropriate bucket; lookup and deletion search within the bucket. Some designs support resizing the number of buckets to rebalance load factors.

Performance and behavior: With a uniform hash distribution and adequate resizing, average-case time for insert, search, and delete approaches O(1). In the worst case, when many keys collide into a single bucket, operations degrade toward O(n). Memory usage depends on the number of buckets and the total number of elements stored.

Variants and use cases: Bucket arrays underlie many hash-table implementations that use separate chaining. They are also used to create sparse arrays, bucketed statistics, and batched processing where items are grouped by buckets for parallelism or cache locality. Variants include fixed-size or dynamically expanding bucket grids and different internal bucket representations.

See also: Hash table, separate chaining, bucket sort, open addressing, and sparse array.