Choose Between an Array and a Linked List

Put arrays and linked lists side by side as implementation options. Describe their time complexity, memory layout, cache behavior, allocation overhead, and iterator or reference stability. Then choose a structure for each of the following scenarios and justify each choice:

1. Many indexed reads over a collection that is mostly fixed.
2. Frequent insertions right after a node that has already been located.
3. A queue containing millions of small elements on current hardware.

Constraints & Assumptions

• Compare a contiguous dynamic array against a standard pointer-based singly or doubly linked list.
• Incorporate real constant factors instead of falling back only on asymptotic notation.
• Specify when the stated linked-list insertion cost leaves out the time required to find the node.

Clarifying Questions to Ask

• Is the collection size known ahead of time or bounded?
• Do references to existing elements need to remain valid after an insertion?
• Are insertions specified by an index or by a handle to an existing node?
• Is memory locality or per-element overhead the limiting resource?

Hint — Split lookup from mutation: An insertion is constant-time only once the place to insert has already been located.

What a Strong Answer Covers

• The costs of indexed access, traversal, insertion, deletion, and resizing.
• Contiguous storage and cache locality as opposed to pointer chasing.
• Per-node pointers, allocator overhead, and fragmentation.
• Nuanced choices for all three scenarios.

Follow-up Questions

• Why might a dynamic array outperform a linked list even when both operations are $O(n)$?
• When does a deque provide an improvement over either choice for queue operations?
• How do intrusive lists change ownership and allocation trade-offs? Overview: Compare arrays and linked lists in terms beyond Big O notation. Address cache locality, allocation and pointer overhead, reference stability, and practical choices for indexed access, insertion, and queues.