1915.Number of Wonderful Substrings
MediumBit ManipulationHash TablePrefix Sum66.8% acceptance2 companiesVideo
With video · 848 results
1927.Sum Game
MediumGame TheoryGreedyMath63.5% acceptance1 companyVideo
1930.Unique Length-3 Palindromic Subsequences
MediumBit ManipulationHash TablePrefix Sum73.8% acceptance6 companiesVideo
1933.Check if String Is Decomposable Into Value-Equal Substrings
EasyString50.4% acceptancePremium elsewhere, free hereVideo
1935.Maximum Number of Words You Can Type
EasyHash TableString82.9% acceptance4 companiesVideo
1941.Check if All Characters Have Equal Number of Occurrences
EasyCountingHash TableString79.4% acceptance4 companiesVideo
1945.Sum of Digits of String After Convert
EasySimulationString74.9% acceptance5 companiesVideo
1946.Largest Number After Mutating Substring
MediumArrayGreedyString38.5% acceptance1 companyVideo
1948.Delete Duplicate Folders in System
HardArrayHash FunctionHash Table77.7% acceptance6 companiesVideo
1957.Delete Characters to Make Fancy String
EasyString74.1% acceptance6 companiesVideo
1960.Maximum Product of the Length of Two Palindromic Substrings
HardHash FunctionRolling HashString32.1% acceptanceVideo
1961.Check If String Is a Prefix of Array
EasyArrayStringTwo Pointers52.7% acceptance1 companyVideo
1963.Minimum Number of Swaps to Make the String Balanced
MediumGreedyStackString78.0% acceptance12 companiesVideo
1967.Number of Strings That Appear as Substrings in Word
EasyArrayString86.1% acceptance6 companiesVideo
1974.Minimum Time to Type Word Using Special Typewriter
EasyGreedyString79.1% acceptance3 companiesVideo
1977.Number of Ways to Separate Numbers
HardDynamic ProgrammingStringSuffix Array21.7% acceptance1 companyVideo
1980.Find Unique Binary String
MediumArrayBacktrackingHash Table81.2% acceptance5 companiesVideo
1985.Find the Kth Largest Integer in the Array
MediumArrayDivide and ConquerHeap (Priority Queue)48.3% acceptance1 companyVideo
1987.Number of Unique Good Subsequences
HardDynamic ProgrammingString52.7% acceptance2 companiesVideo
2000.Reverse Prefix of Word
EasyStackStringTwo Pointers86.3% acceptance5 companiesVideo
2002.Maximum Product of the Length of Two Palindromic Subsequences
MediumBacktrackingBit ManipulationBitmask63.0% acceptance2 companiesVideo
2011.Final Value of Variable After Performing Operations
EasyArraySimulationString90.6% acceptance5 companiesVideo
2014.Longest Subsequence Repeated k Times
HardBacktrackingCountingEnumeration71.3% acceptance3 companiesVideo
2019.The Score of Students Solving Math Expression
HardArrayDynamic ProgrammingMath34.8% acceptance2 companiesVideo
2023.Number of Pairs of Strings With Concatenation Equal to Target
MediumArrayCountingHash Table75.6% acceptance2 companiesVideo
2024.Maximize the Confusion of an Exam
MediumBinary SearchPrefix SumSliding Window70.4% acceptance4 companiesVideo
2027.Minimum Moves to Convert String
EasyGreedyString58.4% acceptance3 companiesVideo
2030.Smallest K-Length Subsequence With Occurrences of a Letter
HardGreedyMonotonic StackStack40.0% acceptance1 companyVideo
2038.Remove Colored Pieces if Both Neighbors are the Same Color
MediumGame TheoryGreedyMath62.8% acceptance3 companiesVideo
2042.Check if Numbers Are Ascending in a Sentence
EasyString73.6% acceptanceVideo
2047.Number of Valid Words in a Sentence
EasyString31.6% acceptance3 companiesVideo
2053.Kth Distinct String in an Array
EasyArrayCountingHash Table82.1% acceptance2 companiesVideo
2055.Plates Between Candles
MediumArrayBinary SearchPrefix Sum47.4% acceptance3 companiesVideo
2056.Number of Valid Move Combinations On Chessboard
HardArrayBacktrackingSimulation48.7% acceptance2 companiesVideo
2060.Check if an Original String Exists Given Two Encoded Strings
HardDynamic ProgrammingString43.6% acceptance2 companiesVideo
2062.Count Vowel Substrings of a String
EasyHash TableString73.6% acceptance12 companiesVideo
2063.Vowels of All Substrings
MediumCombinatoricsDynamic ProgrammingMath55.3% acceptance2 companiesVideo
2067.Number of Equal Count Substrings
MediumCountingPrefix SumString45.1% acceptance1 companyPremium elsewhere, free hereVideo
2068.Check Whether Two Strings are Almost Equivalent
EasyCountingHash TableString64.5% acceptance1 companyVideo
2075.Decode the Slanted Ciphertext
MediumSimulationString67.3% acceptance3 companiesVideo
2083.Substrings That Begin and End With the Same Letter
MediumCountingHash TableMath74.1% acceptancePremium elsewhere, free hereVideo
2085.Count Common Words With One Occurrence
EasyArrayCountingHash Table73.9% acceptance1 companyVideo
2086.Minimum Number of Food Buckets to Feed the Hamsters
MediumDynamic ProgrammingGreedyString48.1% acceptance3 companiesVideo
2096.Step-By-Step Directions From a Binary Tree Node to Another
MediumBinary TreeDepth-First SearchString56.3% acceptance6 companiesVideo
2103.Rings and Rods
EasyHash TableString81.5% acceptance1 companyVideo
2108.Find First Palindromic String in the Array
EasyArrayStringTwo Pointers83.9% acceptanceVideo
2109.Adding Spaces to a String
MediumArraySimulationString71.8% acceptance5 companiesVideo
2114.Maximum Number of Words Found in Sentences
EasyArrayString86.6% acceptance4 companiesVideo
2115.Find All Possible Recipes from Given Supplies
MediumArrayGraphHash Table56.8% acceptance10 companiesVideo
2116.Check if a Parentheses String Can Be Valid
MediumGreedyStackString45.1% acceptance7 companiesVideo
Showing 451–500 of 848
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.