~/problems
Problems
Basics first, then the classics, then company-style assessments. Every problem has tests you run right here; multi-level ones unlock as you go. See the roadmap.
Interview roadmap
Arrays & hashing
Counting, lookups, sorting with keys, prefix sums.
38 problems
Interview roadmap
Arrays & hashing Counting, lookups, sorting with keys, prefix sums.
Complexity analysis guide
- Basics: fast membership with a set basics py · c++ · java easy
- Cross-team handshake energy py · c++ · java easy
- Count distinct values py · c++ · java easy
Hash maps and counting guide
- Basics: count with a dict, then look up basics py · c++ · java easy
- Coffee-shop loyalty stamps easy
- Two Sum py · c++ · java easy
- Contains Duplicate py · c++ · java easy
- Valid Anagram py · c++ · java easy
- Group Anagrams py · c++ · java easy
- Majority Element py · c++ · java easy
- Longest Common Prefix py · c++ · java easy
- Longest Consecutive Sequence py · c++ · java medium
- Encode and Decode Strings medium
- Account registration deduplication Airbnb easy
- Percentage transfers between accounts Coinbase easy
- Full path of a folder Uber py · c++ · java easy
- Compact prefixes of a permutation Uber py · c++ · java medium
- Are two nested sets the same? Pinterest medium
- OA: Sparse Matrix Operation 2 levels OraclePinterest medium
- Turn a tick stream into table rows Jane Street py · c++ · java medium
- Valid Sudoku py · c++ · java medium
- Detect Squares py · c++ · java medium
- First Missing Positive py · c++ · java hard
- Simplified git diff 2 levels Jane Street hard
Sorting, custom keys, coordinate compression guide
- Basics: leaderboard with a tuple sort key basics easy
- Natural order for scanned photos py · c++ · java easy
- Largest Number py · c++ · java medium
- K Closest Points to Origin py · c++ · java easy
- Rank among distinct values py · c++ · java easy
- Sort an Array py · c++ · java medium
Prefix sums and difference arrays guide
- Basics: range sums with a prefix array basics py · c++ · java easy
- Uphill metres between checkpoints py · c++ · java easy
- Range Sum Query 2D Immutable py · c++ · java easy
- Product of Array Except Self py · c++ · java medium
- Seat totals from range bookings py · c++ · java medium
- Count subarrays with a target sum (any sign) py · c++ · java medium
- Count of Stable Subarrays CitadelScale AI py · c++ · java medium
- Max Levels from Each Index Uber py · c++ · java medium