arraybacked

Arraybacked refers to a data structure whose contents are stored in a single contiguous array in memory, rather than in a collection of linked nodes or external storage. This layout offers fast, predictable access patterns and typically good cache locality because neighboring elements are adjacent in memory.

Common examples and usages include dynamic arrays such as Java’s ArrayList, C++’s std::vector, Python’s list, and Rust’s Vec. These structures allocate a contiguous buffer that can hold a sequence of elements and automatically resize as elements are added beyond current capacity.

Key characteristics include constant-time random access by index and efficient iteration due to spatial locality. Append operations are usually amortized O(1); when capacity is exhausted, the backing array is reallocated to a larger size, and existing elements are copied into the new buffer. Insertions or deletions at arbitrary positions typically require shifting elements, resulting in O(n) time in the size of the container.

Trade-offs center on memory management and performance. While array-backed structures offer low per-element overhead and fast access, they may waste unused capacity and incur costly copies during resizing. They also perform poorly for frequent insertions or deletions in the middle compared with node-based structures.

Variants include fixed-size arrays and flexible dynamic arrays that expose capacity separate from size. Applications favoring fast random access and sequential processing generally prefer array-backed implementations over linked structures.

See also: dynamic array, vector, array list, contiguous memory.