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191 problems

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Array578 Dynamic Programming332 String191 Math187 Binary Search136 Hash Table134 Sorting106 Greedy104 Bit Manipulation103 Graph96 Depth-First Search91 Heap (Priority Queue)78 Prefix Sum77 Matrix75 Breadth-First Search71 All topics

Hard · 191 results

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TitleSolutionAcceptDifficultyTopics

10. Regular Expression MatchingVideo

Solution31.8%Hard

Dynamic Programming, Recursion +1· 25 companies

30. Substring with Concatenation of All WordsVideo

Solution35.4%Hard

Hash Table, Sliding Window +1· 10 companies

32. Longest Valid ParenthesesVideo

Solution41.2%Hard

Dynamic Programming, Stack +1· 25 companies

44. Wildcard MatchingVideo

Solution32.8%Hard

Dynamic Programming, Greedy +2· 17 companies

65. Valid NumberVideo

Solution23.3%Hard

String· 7 companies

68. Text JustificationVideo

Solution52.4%Hard

Array, Simulation +1· 44 companies

76. Minimum Window SubstringVideo

Solution48.3%Hard

Hash Table, Sliding Window +1· 35 companies

87. Scramble StringVideo

Solution45.9%Hard

Dynamic Programming, String· 6 companies

115. Distinct SubsequencesVideo

Solution54.1%Hard

Dynamic Programming, String· 13 companies

126. Word Ladder IIVideo

Solution27.7%Hard

Backtracking, Breadth-First Search +2· 15 companies

127. Word LadderVideo

Solution46.3%Hard

Breadth-First Search, Hash Table +1· 41 companies

132. Palindrome Partitioning IIVideo

Solution37.9%Hard

Dynamic Programming, String· 9 companies

140. Word Break IIVideo

Solution56.4%Hard

Array, Backtracking +5· 16 companies

212. Word Search IIVideo

Solution38.8%Hard

Array, Backtracking +3· 21 companies

214. Shortest PalindromeVideo

Solution43.3%Hard

Hash Function, Rolling Hash +2· 8 companies

224. Basic CalculatorVideo

Solution47.3%Hard

Math, Recursion +2· 25 companies

248. Strobogrammatic Number IIIVideoPremium

Solution42.3%Hard

Array, Recursion +1

269. Alien DictionaryVideoPremium

Solution37.1%Hard

Array, Breadth-First Search +4· 18 companies

273. Integer to English WordsVideo

Solution34.9%Hard

Math, Recursion +1· 24 companies

282. Expression Add OperatorsVideo

Solution43.5%Hard

Backtracking, Math +1· 7 companies

297. Serialize and Deserialize Binary TreeVideo

Solution61.1%Hard

Binary Tree, Breadth-First Search +4· 23 companies

301. Remove Invalid ParenthesesVideo

Solution52.4%Hard

Backtracking, Breadth-First Search +1· 10 companies

336. Palindrome PairsVideo

Solution37.7%Hard

Array, Hash Table +2· 8 companies

358. Rearrange String k Distance ApartVideoPremium

Solution39.9%Hard

Counting, Greedy +4· 4 companies

411. Minimum Unique Word AbbreviationVideoPremium

–40.5%Hard

Array, Backtracking +2· 2 companies

420. Strong Password CheckerVideo

Solution16.7%Hard

Greedy, Heap (Priority Queue) +1· 7 companies

425. Word SquaresVideoPremium

Solution54.7%Hard

Array, Backtracking +2· 1 company

428. Serialize and Deserialize N-ary TreeVideoPremium

Solution68.7%Hard

Breadth-First Search, Depth-First Search +2· 7 companies

466. Count The RepetitionsVideo

Solution36.0%Hard

Dynamic Programming, String· 1 company

471. Encode String with Shortest LengthVideoPremium

Solution50.5%Hard

Dynamic Programming, String· 1 company

472. Concatenated WordsVideo

Solution49.9%Hard

Array, Depth-First Search +3· 3 companies

488. Zuma GameVideo

Solution29.4%Hard

Breadth-First Search, Dynamic Programming +3· 7 companies

499. The Maze IIIVideoPremium

Solution52.3%Hard

Array, Breadth-First Search +6· 1 company

514. Freedom TrailVideo

Solution59.4%Hard

Breadth-First Search, Depth-First Search +2· 3 companies

527. Word AbbreviationVideoPremium

Solution62.7%Hard

Array, Greedy +3· 4 companies

564. Find the Closest PalindromeVideo

Solution32.2%Hard

Math, String· 8 companies

588. Design In-Memory File SystemVideoPremium

Solution48.0%Hard

Design, Hash Table +3· 16 companies

591. Tag ValidatorVideo

Solution41.7%Hard

Stack, String· 2 companies

639. Decode Ways IIVideo

Solution32.4%Hard

Dynamic Programming, String· 3 companies

642. Design Search Autocomplete SystemVideoPremium

Solution49.9%Hard

Data Stream, Depth-First Search +5· 12 companies

664. Strange PrinterVideo

Solution61.0%Hard

Dynamic Programming, String· 9 companies

691. Stickers to Spell WordVideo

Solution51.3%Hard

Array, Backtracking +4· 4 companies

726. Number of AtomsVideo

Solution65.1%Hard

Hash Table, Sorting +2· 8 companies

727. Minimum Window SubsequenceVideoPremium

Solution43.5%Hard

Dynamic Programming, Sliding Window +1· 5 companies

730. Count Different Palindromic SubsequencesVideo

Solution48.2%Hard

Dynamic Programming, String· 4 companies

736. Parse Lisp ExpressionVideo

Solution54.1%Hard

Hash Table, Recursion +2· 4 companies

745. Prefix and Suffix SearchVideo

Solution41.2%Hard

Array, Design +3· 3 companies

761. Special Binary StringVideo

Solution79.4%Hard

Recursion, String· 12 companies

770. Basic Calculator IVVideo

Solution49.8%Hard

Hash Table, Math +3· 3 companies

772. Basic Calculator IIIVideoPremium

Solution53.2%Hard

Math, Recursion +2· 16 companies

Showing 1–50 of 191