839.Similar String Groups
HardArrayBreadth-First SearchDepth-First Search56.7% acceptance5 companiesVideo
Hard · 177 results
843.Guess the Word
HardArrayGame TheoryInteractive36.9% acceptance10 companiesVideo
854.K-Similar Strings
HardBreadth-First SearchString41.3% acceptance2 companiesVideo
899.Orderly Queue
HardMathSortingString67.4% acceptance2 companiesVideo
902.Numbers At Most N Given Digit Set
HardArrayBinary SearchDynamic Programming45.9% acceptance4 companiesVideo
903.Valid Permutations for DI Sequence
HardDynamic ProgrammingPrefix SumString56.9% acceptanceVideo
936.Stamping The Sequence
HardGreedyQueueStack62.2% acceptance1 companyVideo
940.Distinct Subsequences II
HardDynamic ProgrammingString56.7% acceptance2 companiesVideo
943.Find the Shortest Superstring
HardArrayBit ManipulationBitmask45.8% acceptance2 companiesVideo
960.Delete Columns to Make Sorted III
HardArrayDynamic ProgrammingString72.7% acceptance2 companiesVideo
972.Equal Rational Numbers
HardMathString47.9% acceptance2 companiesVideo
1028.Recover a Tree From Preorder Traversal
HardBinary TreeDepth-First SearchString83.2% acceptance6 companiesVideo
1032.Stream of Characters
HardArrayData StreamDesign52.8% acceptance4 companiesVideo
1044.Longest Duplicate Substring
HardBinary SearchHash FunctionRolling Hash31.1% acceptance7 companiesVideo
1092.Shortest Common Supersequence
HardDynamic ProgrammingString62.4% acceptance5 companiesVideo
1096.Brace Expansion II
HardBacktrackingBreadth-First SearchStack79.2% acceptance1 companyVideo
1106.Parsing A Boolean Expression
HardRecursionStackString69.8% acceptance8 companiesVideo
1147.Longest Chunked Palindrome Decomposition
HardDynamic ProgrammingGreedyHash Function58.6% acceptance1 companyVideo
1153.String Transforms Into Another String
HardHash TableString34.9% acceptance1 companyPremium elsewhere, free hereVideo
1163.Last Substring in Lexicographical Order
HardStringTwo Pointers35.1% acceptance5 companiesVideo
1178.Number of Valid Words for Each Puzzle
HardArrayBit ManipulationHash Table47.8% acceptance1 companyVideo
1216.Valid Palindrome III
HardDynamic ProgrammingString49.2% acceptance3 companiesPremium elsewhere, free hereVideo
1255.Maximum Score Words Formed by Letters
HardArrayBacktrackingBit Manipulation81.9% acceptance3 companiesVideo
1278.Palindrome Partitioning III
HardDynamic ProgrammingString62.2% acceptanceVideo
1307.Verbal Arithmetic Puzzle
HardArrayBacktrackingMath33.5% acceptance3 companiesVideo
1312.Minimum Insertion Steps to Make a String Palindrome
HardDynamic ProgrammingString74.3% acceptance7 companiesVideo
1316.Distinct Echo Substrings
HardHash FunctionRolling HashString53.7% acceptance1 companyVideo
1320.Minimum Distance to Type a Word Using Two Fingers
HardDynamic ProgrammingString72.2% acceptance2 companiesVideo
1392.Longest Happy Prefix
HardHash FunctionRolling HashString54.1% acceptance6 companiesVideo
1397.Find All Good Strings
HardDynamic ProgrammingStringString Matching46.4% acceptance2 companiesVideo
1416.Restore The Array
HardDynamic ProgrammingString47.2% acceptance2 companiesVideo
1505.Minimum Possible Integer After at Most K Adjacent Swaps On Digits
HardBinary Indexed TreeGreedySegment Tree41.8% acceptance1 companyVideo
1520.Maximum Number of Non-Overlapping Substrings
HardGreedyString65.0% acceptance1 companyVideo
1531.String Compression II
HardDynamic ProgrammingString52.2% acceptance5 companiesVideo
1542.Find Longest Awesome Substring
HardBit ManipulationHash TableString47.4% acceptance1 companyVideo
1585.Check If String Is Transformable With Substring Sort Operations
HardGreedySortingString51.9% acceptance1 companyVideo
1639.Number of Ways to Form a Target String Given a Dictionary
HardArrayDynamic ProgrammingString56.6% acceptance9 companiesVideo
1745.Palindrome Partitioning IV
HardDynamic ProgrammingString45.8% acceptance1 companyVideo
1771.Maximize Palindrome Length From Subsequences
HardDynamic ProgrammingString39.0% acceptance1 companyVideo
1830.Minimum Number of Operations to Make String Sorted
HardCombinatoricsMathString51.0% acceptance1 companyVideo
1842.Next Palindrome Using Same Digits
HardStringTwo Pointers54.2% acceptance1 companyPremium elsewhere, free hereVideo
1896.Minimum Cost to Change the Final Value of Expression
HardDynamic ProgrammingMathStack50.0% acceptance1 companyVideo
1948.Delete Duplicate Folders in System
HardArrayHash FunctionHash Table77.7% acceptance6 companiesVideo
1960.Maximum Product of the Length of Two Palindromic Substrings
HardHash FunctionRolling HashString32.1% acceptanceVideo
1977.Number of Ways to Separate Numbers
HardDynamic ProgrammingStringSuffix Array21.7% acceptance1 companyVideo
1987.Number of Unique Good Subsequences
HardDynamic ProgrammingString52.7% acceptance2 companiesVideo
2014.Longest Subsequence Repeated k Times
HardBacktrackingCountingEnumeration71.3% acceptance3 companiesVideo
2019.The Score of Students Solving Math Expression
HardArrayDynamic ProgrammingMath34.8% acceptance2 companiesVideo
2030.Smallest K-Length Subsequence With Occurrences of a Letter
HardGreedyMonotonic StackStack40.0% acceptance1 companyVideo
2056.Number of Valid Move Combinations On Chessboard
HardArrayBacktrackingSimulation48.7% acceptance2 companiesVideo
Showing 51–100 of 177
How to use these solutions
Each solution breaks the problem into approaches, usually from brute force to the best one, and explains why each works. Code comes in Python, Java, C++ and other languages. Knowing why an approach works matters more in an interview than remembering the code.
- Try the problem first. Give it at least 20 minutes before you open the solution.
- Read every approach. The brute force shows you the problem; the faster ones show the pattern.
- Check the complexity. Note the time and space of each approach and what makes the difference.
- Write it yourself. Close the solution and code it from memory in the editor.
- Come back in a week. Solving it again later is what makes the pattern stick.