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iterator

5 problems

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iterator is one of the most repeated interview dimensions. Start with edge-safe fundamentals, then move into pattern-level trade-offs.

Interview Signal

Frequently tests problem modeling, edge handling, and verbal clarity.

Common Pitfall

Template-only answers break under follow-up questioning.

Practice Strategy

Practice in 3-5 problem rounds and always review complexity alternatives.

Recommended Progression

Foundation

Pattern Bridge

High-Pressure Round

Problem bank

iterator problem bank

Start with a compact scan-friendly list and progressively load more so the topic page stays readable even when the corpus is large.

Progressive topic library

Built for large topic sets: scan the structure first, then go deeper.

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tuneDifficulty

Showing 5 / 5 problems

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173

Binary Search Tree Iterator

Implement an iterator for in-order traversal of a binary search tree (BST), maintaining traversal state with stack-based…

Medium

stack

284

Peeking Iterator

Design an iterator with peek functionality, adding to the standard next and hasNext operations for efficient element acc…

Medium

array

341

Flatten Nested List Iterator

Implement an iterator to flatten a nested list of integers, accounting for potential nesting levels.

Medium

stack

900

RLE Iterator

Design an efficient iterator for a run-length encoded array, handling large counts and sequential access correctly every…

Medium

array

1286

Iterator for Combination

Implement an iterator that generates all combinations of a given length using efficient backtracking with pruning.

Medium

string

Related Patterns

Binary-tree traversal and state tracking

2 linked problems

Array plus Design

2 linked problems

Backtracking search with pruning

1 linked problems