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🧮 Interview Prep

Core Algorithms

Arrays, strings, hash maps, two pointers, sliding windows, stacks, binary search and linked lists: the coding rounds at almost every company.

📘 Learn it from scratch

Visual, hands-on lessons for every pattern in this topic. Do the lesson, then come back and the questions click.

Hash Maps & SetsTwo Pointers & StacksThe Sliding Window PatternThe Monotonic StackBinary SearchLinked ListsPrefix SumsIntervalsGreedy AlgorithmsSorting Algorithms, VisualizedBit ManipulationGrids & Matrix TraversalDesigning Data Structures

100 questions, most asked first

Ranked by how often each question comes up in real interviews. #1 is the most common.

Any difficulty Easy Medium Hard

All patterns Hash map Stack Greedy Intervals Sliding window Prefix sum Two pointers Linked list Binary search Design Monotonic stack Matrix Sorting Bits & math

Unlock 6 more Core Algorithms questions · all 1,200 questions for $39/year (about 11¢ a day)See full access #22Trapping Rain WaterTwo pointersHard🔒#34Minimum Window SubstringSliding windowHard🔒#50Largest Rectangle in HistogramMonotonic stackHard🔒#53Median of Two Sorted ArraysBinary searchHard🔒#58Merge K Sorted ListsLinked listHard🔒#61Sliding Window MaximumMonotonic stackHard🔒