What is the typical structure of a node in a singly linked list, and how does memory layout differ from an array?

• A. A node stores a data value and a next pointer; memory is non-contiguous because nodes are allocated separately, unlike an array where elements are stored contiguously and support random access.
• B. A node stores only a data value; memory is contiguous; arrays store values behind a single pointer.
• C. A node stores a data value and a previous pointer; memory is contiguous.
• D. A node stores data, a next pointer, and an index field; memory is non-contiguous.

Answer: (A)

In a singly linked list, each node stores a data value and a pointer to the next node. This creates a chain where nodes are linked by addresses rather than being stored in one block of memory. Because every node is allocated separately, the overall layout is non-contiguous, and following the list requires visiting each node via its next pointer rather than jumping to a known index.

This is different from an array, where elements are placed one after another in a single, contiguous block of memory. That contiguity lets you access any element directly by its index (constant-time random access) and benefits from better cache locality.

So the typical node structure is data plus a next pointer, and the memory layout is non-contiguous, unlike arrays.

The other descriptions don’t fit: a node that holds only data lacks the link to the rest of the list; a previous pointer would describe a doubly linked list; and an index field is not part of the standard singly linked list node structure and would imply a different approach.