Snapshot Set with Stable Iterators

Implement a SnapshotSet<T>: interface SnapshotSet<T> { void add(T e); void remove(T e); boolean contains(T e); Iterator<T> iterator(); } Requirements: contains(e) queries membership in the current set. iterator() returns an iterator over a snapshot of the set at the moment the iterator is created. Any add/remove after an iterator is created must not affect what that iterator yields; however, it must affect contains and any iterators created later. No ordering guarantee is required, but an iterator must not return duplicates and must not miss any element that belongs to its snapshot. Implement add/remove/contains/iterator (Java or clear pseudocode). Also explain expected outputs for this scenario (order doesn’t matter, set contents do): Start: add(5), add(2), add(8) it = iterator() (created but not consumed) remove(5), then contains(2) should be true remove(2), then contains(2) should be false add(2) it2 = iterator() it should iterate elements from the snapshot it captured; it2 should iterate elements from its own snapshot. Note: The post suggests “snapshot set; old iterators must still be able to iterate.” Clarify with the interviewer whether this is a strong snapshot (fully isolated) or a weaker guarantee. Example Input add 5 add 2 add 8 iter it remove 5 contains 2 remove 2 contains 2 add 2 iter it2 consume it consume it2 Output contains(2)=true contains(2)=false it yields {5,2,8} (order arbitrary) if strong snapshot it2 yields {2,8} (order arbitrary)