A collection-contract self-check tests ordering, membership, backed views and the cost of access patterns.
Review the contracts
Review collection choices, backed views, comparison rules before answering.
Choose and explain an answer
Name the implementation as well as the interface. Determine whether the returned data is a view, a shallow snapshot or independently owned values.
Select an answer for every question, then check the result and read each explanation. Progress remains in this browser; this is a self-check, not a judged program submission or a credential.
Common Mistakes
Priority removal does not imply sorted iteration. Copying membership does not copy mutable element state.