#iterators

7 iterators interview questions, asked at Google, OpenAI, Airbnb and 6 more companies. Last asked Sep 2026.

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Split a file iterator into balanced line-aligned partsCodingSplit a large file into balanced parts for parallel workers without cutting lines in half: each part holds whole lines and the parts stay close in size. Reported on 1point3acres'…
Last asked Sep 2026
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Snapshot set with frozen insertion-order iteratorsCodingImplement SnapshotSet, a set of integers whose iterators are frozen at the moment they are created. - add(value) - bool: insert value. Return False and do nothing if it is already…
Last asked Sep 2026
Lazy tee iteratorCodingImplement tee in Python: from one source iterator, create n independent iterators that each yield the full sequence. Pull from the source only when some copy needs the next item…
Last asked Aug 2026
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Resumable iterators that save and restore their positionCodingDefine an iterator interface that can export its state and be resumed from it later. Implement it for a flat list, then for nested multi-dimensional lists, then across several…
Last asked Jun 2026
Flatten a nested list iteratorCodingA list holds integers and other lists, nested to any depth. Write an iterator with next() and hasnext() that returns the integers in order. Do it lazily with a stack of positions…
Last asked Apr 2026
Lazy in-order BST iteratorCodingWrite an iterator over a binary search tree that returns values in sorted order one at a time, with next() and hasnext(). Do it lazily with a stack, so memory is proportional to…
Last asked Feb 2026
Binary search tree iteratorCodingImplement an iterator over a binary search tree that returns the values in ascending order with next() and hasnext(). Each call should take amortised O(1) time, and memory should…
Last asked Jan 2026