Arrayimplementering

Arrayimplementering refers to the methods and structures used to allocate, store, and access arrays within a programming language or runtime. At its core, an array provides indexed, contiguous storage for elements of the same type, enabling constant-time element access through address calculation based on a base address and the element size.

In most implementations, arrays are laid out contiguously in memory. This means that the i-th element is located at base + i * element_size. This layout yields fast random access and good cache locality, but affects how the array can grow. Fixed-size arrays have a predetermined capacity and do not resize automatically, while dynamic arrays maintain both a size and a capacity, growing when needed (commonly by doubling the capacity) and re-copying elements into a larger block.

Operations and costs vary by implementation. Access by index is typically O(1). Insertion or deletion at the end can be O(1) amortized for dynamic arrays, while insertions or deletions in the middle are O(n) due to shifting elements. Resizing incurs a potentially expensive copy, but the amortized cost per element remains small because resizing happens infrequently relative to insertions.

Language-specific differences influence array implementation. C/C++ offers fixed-size arrays and a dynamic vector-like structure (std::vector) built on contiguous memory. Java stores arrays as objects with a length field. Python’s lists and JavaScript arrays are dynamic arrays of references or values, with additional language-level handling. Multi-dimensional arrays may be implemented as arrays of arrays or as a single contiguous block using row-major or column-major order.

Overall, arrayimplementering balances memory overhead, growth strategy, and access performance, shaping the efficiency of algorithms that rely on indexed storage.