Which statement correctly describes arrays and linked lists in terms of memory layout and performance?

• A. Arrays have contiguous memory, O(1) random access, insert/delete O(n); Linked lists store elements with pointers, non-contiguous memory, O(n) random access, insert/delete O(1) with a predecessor reference.
• B. Arrays are always faster for all operations.
• C. Linked lists have contiguous memory and O(1) random access.
• D. Arrays require dynamic resizing for every insert.

Answer: (D)

The main idea here is how memory layout affects access and update times for two common data structures. Arrays store elements in a single, continuous block of memory, which lets you jump straight to any index in constant time. That direct access is why arrays are fast for lookups by position. But keeping the array contiguous means inserting or deleting somewhere other than the end usually requires shifting a bunch of elements, which takes time proportional to the number of elements moved.

Linked lists, on the other hand, consist of nodes scattered around in memory with pointers connecting them. There isn’t a fast way to jump to the i-th element without following pointers from the start, so random access is O(n). However, once you’re at a known node (and, in a typical singly linked list, with access to its predecessor), inserting or deleting a node is O(1) because you only relink a couple of pointers.

The statement about dynamic resizing for every insert isn’t accurate for most practical dynamic-array implementations. They allocate extra space and resize only when needed, so insertions aren’t required to resize every time, and the amortized cost stays efficient.

So the description that best captures the real trade-offs is: arrays have contiguous memory with O(1) random access but insertion/deletion is O(n) due to shifting; linked lists use non-contiguous memory with O(n) random access but O(1) insertions/deletions when you have the relevant node and its predecessor.