13.Roman to Integer
EasyHash TableMathString67.0% acceptance36 companiesVideo
Easy · 249 results
14.Longest Common Prefix
EasyStringTrie48.6% acceptance60 companiesVideo
20.Valid Parentheses
EasyStackString45.2% acceptance113 companiesVideo
28.Find the Index of the First Occurrence in a String
EasyStringString MatchingTwo Pointers47.0% acceptance16 companiesVideo
58.Length of Last Word
EasyString59.7% acceptance7 companiesVideo
67.Add Binary
EasyBit ManipulationMathSimulation58.4% acceptance17 companiesVideo
125.Valid Palindrome
EasyStringTwo Pointers54.2% acceptance39 companiesVideo
168.Excel Sheet Column Title
EasyMathString47.9% acceptance10 companiesVideo
171.Excel Sheet Column Number
EasyMathString68.6% acceptance9 companiesVideo
205.Isomorphic Strings
EasyHash TableString48.8% acceptance15 companiesVideo
242.Valid Anagram
EasyHash TableSortingString68.5% acceptance40 companiesVideo
243.Shortest Word Distance
EasyArrayString66.3% acceptance8 companiesPremium elsewhere, free hereVideo
246.Strobogrammatic Number
EasyHash TableStringTwo Pointers47.6% acceptance2 companiesPremium elsewhere, free hereVideo
257.Binary Tree Paths
EasyBacktrackingBinary TreeDepth-First Search69.5% acceptance8 companiesVideo
266.Palindrome Permutation
EasyBit ManipulationHash TableString68.6% acceptance5 companiesPremium elsewhere, free hereVideo
290.Word Pattern
EasyHash TableString44.5% acceptance9 companiesVideo
293.Flip Game
EasyString64.8% acceptance1 companyPremium elsewhere, free hereVideo
344.Reverse String
EasyStringTwo Pointers81.2% acceptance16 companiesVideo
345.Reverse Vowels of a String
EasyStringTwo Pointers62.7% acceptance13 companiesVideo
383.Ransom Note
EasyCountingHash TableString66.3% acceptance14 companiesVideo
387.First Unique Character in a String
EasyCountingHash TableQueue66.4% acceptance25 companiesVideo
389.Find the Difference
EasyBit ManipulationHash TableSorting60.8% acceptance6 companiesVideo
392.Is Subsequence
EasyDynamic ProgrammingStringTwo Pointers49.5% acceptance16 companiesVideo
408.Valid Word Abbreviation
EasyStringTwo Pointers37.0% acceptance7 companiesPremium elsewhere, free hereVideo
409.Longest Palindrome
EasyGreedyHash TableString55.9% acceptance8 companiesVideo
412.Fizz Buzz
EasyMathSimulationString75.9% acceptance18 companiesVideo
415.Add Strings
EasyMathSimulationString52.1% acceptance14 companiesVideo
434.Number of Segments in a String
EasyString37.6% acceptance3 companiesVideo
459.Repeated Substring Pattern
EasyStringString Matching48.6% acceptance9 companiesVideo
482.License Key Formatting
EasyString46.4% acceptance1 companyVideo
500.Keyboard Row
EasyArrayHash TableString74.3% acceptance4 companiesVideo
520.Detect Capital
EasyString56.8% acceptance4 companiesVideo
521.Longest Uncommon Subsequence I
EasyString62.7% acceptance2 companiesVideo
541.Reverse String II
EasyStringTwo Pointers54.7% acceptance7 companiesVideo
551.Student Attendance Record I
EasyString50.1% acceptance3 companiesVideo
557.Reverse Words in a String III
EasyStringTwo Pointers84.0% acceptance7 companiesVideo
599.Minimum Index Sum of Two Lists
EasyArrayHash TableString60.8% acceptance4 companiesVideo
604.Design Compressed String Iterator
EasyArrayDesignIterator40.5% acceptance1 companyPremium elsewhere, free hereVideo
657.Robot Return to Origin
EasySimulationString78.0% acceptance5 companiesVideo
680.Valid Palindrome II
EasyGreedyStringTwo Pointers44.7% acceptance16 companiesVideo
696.Count Binary Substrings
EasyStringTwo Pointers70.3% acceptance18 companiesVideo
709.To Lower Case
EasyString84.8% acceptance3 companiesVideo
734.Sentence Similarity
EasyArrayHash TableString44.5% acceptance1 companyPremium elsewhere, free hereVideo
748.Shortest Completing Word
EasyArrayHash TableString63.5% acceptance1 companyVideo
771.Jewels and Stones
EasyHash TableString89.5% acceptance6 companiesVideo
796.Rotate String
EasyStringString Matching66.6% acceptance12 companiesVideo
800.Similar RGB Color
EasyEnumerationMathString68.6% acceptance1 companyPremium elsewhere, free hereVideo
804.Unique Morse Code Words
EasyArrayHash TableString83.6% acceptance3 companiesVideo
806.Number of Lines To Write String
EasyArrayString72.9% acceptance2 companiesVideo
819.Most Common Word
EasyArrayCountingHash Table45.0% acceptance5 companiesVideo
Showing 1–50 of 249
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.