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    Maximal SquareNot Completed

    Solutions: 1894 | View user solutions | Added 05/21/16

    Pentagonal NumberNot Completed

    Solutions: 1992 | View user solutions | Added 08/31/16

    Eight QueensNot Completed

    Solutions: 1575 | View user solutions | Added 11/06/16

    Free Challenges

    Longest WordNot Completed

    Solutions: 83223 | Step-by-step solution | Challenge discussion

    First FactorialNot Completed

    Solutions: 107812 | Step-by-step solution | Challenge discussion

    First ReverseNot Completed

    Solutions: 127651 | Step-by-step solution | Challenge discussion

    Letter ChangesNot Completed

    Solutions: 79804 | Step-by-step solution | Challenge discussion

    Simple AddingNot Completed

    Solutions: 64916 | Step-by-step solution | Challenge discussion

    Letter CapitalizeNot Completed

    Solutions: 55223 | Step-by-step solution | Challenge discussion

    Simple SymbolsNot Completed

    Solutions: 46945 | Step-by-step solution | Challenge discussion

    Check NumsNot Completed

    Solutions: 47488 | Step-by-step solution | Challenge discussion

    Time ConvertNot Completed

    Solutions: 36250 | Step-by-step solution | Challenge discussion

    Alphabet SoupNot Completed

    Solutions: 33212 | Step-by-step solution | Challenge discussion

    Kaprekars ConstantNot Completed

    Solutions: 6241 | View all user solutions | Challenge discussion

    Chessboard TravelingNot Completed

    Solutions: 2715 | View all user solutions | Challenge discussion

    Maximal SquareNot Completed

    Solutions: 1894 | View all user solutions | Challenge discussion

    Pentagonal NumberNot Completed

    Solutions: 1992 | View all user solutions | Challenge discussion

    Correct PathNot Completed

    Solutions: 1927 | View all user solutions | Challenge discussion

    Scale BalancingNot Completed

    Solutions: 2646 | View all user solutions | Challenge discussion

    Vowel SquareNot Completed

    Solutions: 1708 | View all user solutions | Challenge discussion

    Eight QueensNot Completed

    Solutions: 1575 | View all user solutions | Challenge discussion

    Closest Enemy IINot Completed

    Solutions: 1543 | View all user solutions | Challenge discussion

    Questions MarksNot Completed

    Solutions: 4443 | View all user solutions | Challenge discussion

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    Easy Difficulty

    First ReverseNot Completed

    Solutions: 127651 | Step-by-step solution | Challenge discussion

    First FactorialNot Completed

    Solutions: 107812 | Step-by-step solution | Challenge discussion

    Longest WordNot Completed

    Solutions: 83223 | Step-by-step solution | Challenge discussion

    Letter ChangesNot Completed

    Solutions: 79804 | Step-by-step solution | Challenge discussion

    Simple AddingNot Completed

    Solutions: 64916 | Step-by-step solution | Challenge discussion

    Letter CapitalizeNot Completed

    Solutions: 55223 | Step-by-step solution | Challenge discussion

    Simple SymbolsNot Completed

    Solutions: 46945 | Step-by-step solution | Challenge discussion

    Check NumsNot Completed

    Solutions: 47488 | Step-by-step solution | Challenge discussion

    Time ConvertNot Completed

    Solutions: 36250 | Step-by-step solution | Challenge discussion

    Alphabet SoupNot Completed

    Solutions: 33212 | Step-by-step solution | Challenge discussion

    AB CheckNot Completed

    Solutions: 17225 | Step-by-step solution | Challenge discussion

    Vowel CountNot Completed

    Solutions: 15819 | Step-by-step solution | Challenge discussion

    Word CountNot Completed

    Solutions: 14924 | Step-by-step solution | Challenge discussion

    Ex OhNot Completed

    Solutions: 14632 | Step-by-step solution | Challenge discussion

    PalindromeNot Completed

    Solutions: 17061 | Step-by-step solution | Challenge discussion

    Arith GeoNot Completed

    Solutions: 13599 | Step-by-step solution | Challenge discussion

    Array Addition INot Completed

    Solutions: 8806 | Step-by-step solution | Challenge discussion

    Letter Count INot Completed

    Solutions: 8032 | Step-by-step solution | Challenge discussion

    Second GreatLowNot Completed

    Solutions: 13308 | Step-by-step solution | Challenge discussion

    Division StringifiedNot Completed

    Solutions: 9940 | Step-by-step solution | Challenge discussion

    Counting Minutes INot Completed

    Solutions: 5929 | Step-by-step solution | Challenge discussion

    Mean ModeNot Completed

    Solutions: 7719 | Step-by-step solution | Challenge discussion

    Dash InsertNot Completed

    Solutions: 8762 | Step-by-step solution | Challenge discussion

    Swap CaseNot Completed

    Solutions: 8258 | Step-by-step solution | Challenge discussion

    Number AdditionNot Completed

    Solutions: 8171 | Step-by-step solution | Challenge discussion

    Third GreatestNot Completed

    Solutions: 7565 | Step-by-step solution | Challenge discussion

    Powers of TwoNot Completed

    Solutions: 8450 | Step-by-step solution | Challenge discussion

    Additive PersistenceNot Completed

    Solutions: 6038 | Step-by-step solution | Challenge discussion

    Multiplicative PersistenceNot Completed

    Solutions: 4640 | Step-by-step solution | Challenge discussion

    Off Line MinimumNot Completed

    Solutions: 6262 | Step-by-step solution | Challenge discussion

    Changing SequenceNot Completed

    Solutions: 2646 | Step-by-step solution | Challenge discussion

    Overlapping RangesNot Completed

    Solutions: 2657 | Step-by-step solution | Challenge discussion

    SuperincreasingNot Completed

    Solutions: 2711 | Step-by-step solution | Challenge discussion

    Hamming DistanceNot Completed

    Solutions: 1857 | Step-by-step solution | Challenge discussion

    Rectangle AreaNot Completed

    Solutions: 2251 | Step-by-step solution | Challenge discussion

    Bitwise OneNot Completed

    Solutions: 1830 | Step-by-step solution | Challenge discussion

    Other ProductsNot Completed

    Solutions: 1905 | Step-by-step solution | Challenge discussion

    Wave SortingNot Completed

    Solutions: 1311 | Step-by-step solution | Challenge discussion

    Array MatchingNot Completed

    Solutions: 1639 | Step-by-step solution | Challenge discussion

    Binary ReversalNot Completed

    Solutions: 1347 | Step-by-step solution | Challenge discussion

    Longest Increasing SequenceNot Completed

    Solutions: 1315 | Step-by-step solution | Challenge discussion

    Even PairsNot Completed

    Solutions: 1241 | Step-by-step solution | Challenge discussion

    Next PalindromeNot Completed

    Solutions: 1086 | Step-by-step solution | Challenge discussion

    Largest PairNot Completed

    Solutions: 1435 | Step-by-step solution | Challenge discussion

    Nonrepeating CharacterNot Completed

    Solutions: 1108 | Step-by-step solution | Challenge discussion

    Two SumNot Completed

    Solutions: 1993 | Step-by-step solution | Challenge discussion

    Bitwise TwoNot Completed

    Solutions: 779 | Step-by-step solution | Challenge discussion

    Power Set CountNot Completed

    Solutions: 1117 | Step-by-step solution | Challenge discussion

    Product DigitsNot Completed

    Solutions: 1394 | Step-by-step solution | Challenge discussion

    Palindrome CreatorNot Completed

    Solutions: 1198 | Step-by-step solution | Challenge discussion

    Basic Roman NumeralsNot Completed

    Solutions: 779 | Step-by-step solution | Challenge discussion

    Food DistributionNot Completed

    Solutions: 702 | Step-by-step solution | Challenge discussion

    Three SumNot Completed

    Solutions: 805 | Step-by-step solution | Challenge discussion

    Correct PathNot Completed

    Solutions: 1927 | Step-by-step solution | Challenge discussion

    Scale BalancingNot Completed

    Solutions: 2646 | Step-by-step solution | Challenge discussion

    Three NumbersNot Completed

    Solutions: 790 | Step-by-step solution | Challenge discussion

    Alphabet SearchingNot Completed

    Solutions: 658 | Step-by-step solution | Challenge discussion

    Time DifferenceNot Completed

    Solutions: 429 | Step-by-step solution | Challenge discussion

    Triangle RowNot Completed

    Solutions: 404 | Step-by-step solution | Challenge discussion

    Vowel SquareNot Completed

    Solutions: 1708 | Step-by-step solution | Challenge discussion

    Closest EnemyNot Completed

    Solutions: 629 | Step-by-step solution | Challenge discussion

    Closest Enemy IINot Completed

    Solutions: 1543 | Step-by-step solution | Challenge discussion

    Number StreamNot Completed

    Solutions: 431 | Step-by-step solution | Challenge discussion

    Largest FourNot Completed

    Solutions: 608 | Step-by-step solution | Challenge discussion

    Distinct CharactersNot Completed

    Solutions: 449 | Step-by-step solution | Challenge discussion

    Questions MarksNot Completed

    Solutions: 4443 | Step-by-step solution | Challenge discussion

    Camel CaseNot Completed

    Solutions: 527 | Step-by-step solution | Challenge discussion

    ASCII ConversionNot Completed

    Solutions: 369 | Step-by-step solution | Challenge discussion

    Simple EvensNot Completed

    Solutions: 503 | Step-by-step solution | Challenge discussion

    Snake CaseNot Completed

    Solutions: 430 | Step-by-step solution | Challenge discussion

    Sum MultiplierNot Completed

    Solutions: 537 | Step-by-step solution | Challenge discussion

    String MergeNot Completed

    Solutions: 512 | Step-by-step solution | Challenge discussion

    One DecrementedNot Completed

    Solutions: 477 | Step-by-step solution | Challenge discussion

    Element MergerNot Completed

    Solutions: 505 | Step-by-step solution | Challenge discussion

    GCFNot Completed

    Solutions: 476 | Step-by-step solution | Challenge discussion

    Serial NumberNot Completed

    Solutions: 639 | Step-by-step solution | Challenge discussion

    String PeriodsNot Completed

    Solutions: 535 | Step-by-step solution | Challenge discussion

    Palindrome SwapperNot Completed

    Solutions: 351 | Step-by-step solution | Challenge discussion

    Remove BracketsNot Completed

    Solutions: 505 | Step-by-step solution | Challenge discussion

    Command LineNot Completed

    Solutions: 226 | Step-by-step solution | Challenge discussion

    Star RatingNot Completed

    Solutions: 487 | Step-by-step solution | Challenge discussion

    Moving MedianNot Completed

    Solutions: 205 | Step-by-step solution | Challenge discussion

    Group TotalsNot Completed

    Solutions: 217 | Step-by-step solution | Challenge discussion

    String ChangesNot Completed

    Solutions: 87 | Step-by-step solution | Challenge discussion

    FizzBuzzNot Completed

    Solutions: 140 | Step-by-step solution | Challenge discussion

    H DistanceNot Completed

    Solutions: 80 | Step-by-step solution | Challenge discussion

    Different CasesNot Completed

    Solutions: 90 | Step-by-step solution | Challenge discussion

    Medium Difficulty

    Prime TimeNot Completed

    Solutions: 12166 | Step-by-step solution | Challenge discussion

    Run Length Not Completed

    Solutions: 8695 | Step-by-step solution | Challenge discussion

    Prime MoverNot Completed

    Solutions: 7513 | Step-by-step solution | Challenge discussion

    Palindrome TwoNot Completed

    Solutions: 7221 | Step-by-step solution | Challenge discussion

    DivisionNot Completed

    Solutions: 6705 | Step-by-step solution | Challenge discussion

    String ScrambleNot Completed

    Solutions: 7379 | Step-by-step solution | Challenge discussion

    Arith Geo IINot Completed

    Solutions: 5051 | Step-by-step solution | Challenge discussion

    Array AdditionNot Completed

    Solutions: 4524 | Step-by-step solution | Challenge discussion

    Binary ConverterNot Completed

    Solutions: 4580 | Step-by-step solution | Challenge discussion

    Letter CountNot Completed

    Solutions: 4538 | Step-by-step solution | Challenge discussion

    Caesar CipherNot Completed

    Solutions: 5212 | Step-by-step solution | Challenge discussion

    Simple ModeNot Completed

    Solutions: 5056 | Step-by-step solution | Challenge discussion

    ConsecutiveNot Completed

    Solutions: 4149 | Step-by-step solution | Challenge discussion

    Formatted DivisionNot Completed

    Solutions: 3851 | Step-by-step solution | Challenge discussion

    Counting MinutesNot Completed

    Solutions: 2826 | View all user solutions | Challenge discussion

    Permutation StepNot Completed

    Solutions: 3375 | View all user solutions | Challenge discussion

    Prime CheckerNot Completed

    Solutions: 2591 | View all user solutions | Challenge discussion

    Dash Insert IINot Completed

    Solutions: 4974 | View all user solutions | Challenge discussion

    Swap IINot Completed

    Solutions: 2777 | View all user solutions | Challenge discussion

    Number SearchNot Completed

    Solutions: 3401 | View all user solutions | Challenge discussion

    Triple DoubleNot Completed

    Solutions: 3151 | View all user solutions | Challenge discussion

    Bracket MatcherNot Completed

    Solutions: 2877 | View all user solutions | Challenge discussion

    String ReductionNot Completed

    Solutions: 2373 | View all user solutions | Challenge discussion

    ThreeFive MultiplesNot Completed

    Solutions: 2870 | View all user solutions | Challenge discussion

    Binary Search Tree LCANot Completed

    Solutions: 303 | View all user solutions | Challenge discussion

    Coin DeterminerNot Completed

    Solutions: 2338 | View all user solutions | Challenge discussion

    Fibonacci CheckerNot Completed

    Solutions: 2675 | View all user solutions | Challenge discussion

    Multiple BracketsNot Completed

    Solutions: 2392 | View all user solutions | Challenge discussion

    Most Free TimeNot Completed

    Solutions: 1449 | View all user solutions | Challenge discussion

    Overlapping RectanglesNot Completed

    Solutions: 1637 | View all user solutions | Challenge discussion

    Look Say SequenceNot Completed

    Solutions: 1503 | View all user solutions | Challenge discussion

    Distinct ListNot Completed

    Solutions: 2427 | View all user solutions | Challenge discussion

    Number EncodingNot Completed

    Solutions: 1508 | View all user solutions | Challenge discussion

    Stock PickerNot Completed

    Solutions: 763 | View all user solutions | Challenge discussion

    Max SubarrayNot Completed

    Solutions: 686 | View all user solutions | Challenge discussion

    Missing DigitNot Completed

    Solutions: 467 | View all user solutions | Challenge discussion

    K Unique CharactersNot Completed

    Solutions: 479 | View all user solutions | Challenge discussion

    Bitmap HolesNot Completed

    Solutions: 344 | View all user solutions | Challenge discussion

    Symmetric TreeNot Completed

    Solutions: 302 | View all user solutions | Challenge discussion

    Binary Tree LCANot Completed

    Solutions: 168 | View all user solutions | Challenge discussion

    LRU CacheNot Completed

    Solutions: 209 | View all user solutions | Challenge discussion

    Tree ConstructorNot Completed

    Solutions: 310 | View all user solutions | Challenge discussion

    Array Min JumpsNot Completed

    Solutions: 253 | View all user solutions | Challenge discussion

    Nearest Smaller ValuesNot Completed

    Solutions: 441 | View all user solutions | Challenge discussion

    Matrix SpiralNot Completed

    Solutions: 212 | View all user solutions | Challenge discussion

    Word SplitNot Completed

    Solutions: 389 | View all user solutions | Challenge discussion

    Pair SearchingNot Completed

    Solutions: 127 | View all user solutions | Challenge discussion

    Boggle SolverNot Completed

    Solutions: 109 | View all user solutions | Challenge discussion

    HTML ElementsNot Completed

    Solutions: 172 | View all user solutions | Challenge discussion

    Missing Digit IINot Completed

    Solutions: 162 | View all user solutions | Challenge discussion

    Palindromic SubstringNot Completed

    Solutions: 271 | View all user solutions | Challenge discussion

    Trapping WaterNot Completed

    Solutions: 165 | View all user solutions | Challenge discussion

    Matrix PathNot Completed

    Solutions: 87 | View all user solutions | Challenge discussion

    Seating StudentsNot Completed

    Solutions: 163 | View all user solutions | Challenge discussion

    Longest Matrix PathNot Completed

    Solutions: 78 | View all user solutions | Challenge discussion

    Min Window SubstringNot Completed

    Solutions: 170 | View all user solutions | Challenge discussion

    Matrix ChainsNot Completed

    Solutions: 70 | View all user solutions | Challenge discussion

    Histogram AreaNot Completed

    Solutions: 122 | View all user solutions | Challenge discussion

    Matching CharactersNot Completed

    Solutions: 195 | View all user solutions | Challenge discussion

    Ternary ConverterNot Completed

    Solutions: 98 | View all user solutions | Challenge discussion

    Linear CongruenceNot Completed

    Solutions: 59 | View all user solutions | Challenge discussion

    Formatted NumberNot Completed

    Solutions: 205 | View all user solutions | Challenge discussion

    Largest Row ColumnNot Completed

    Solutions: 57 | View all user solutions | Challenge discussion

    Eight QueensNot Completed

    Solutions: 1575 | View all user solutions | Challenge discussion

    Three PointsNot Completed

    Solutions: 144 | View all user solutions | Challenge discussion

    Character RemovalNot Completed

    Solutions: 156 | View all user solutions | Challenge discussion

    Simple PasswordNot Completed

    Solutions: 203 | View all user solutions | Challenge discussion

    Preorder TraversalNot Completed

    Solutions: 95 | View all user solutions | Challenge discussion

    String ZigzagNot Completed

    Solutions: 103 | View all user solutions | Challenge discussion

    Off BinaryNot Completed

    Solutions: 87 | View all user solutions | Challenge discussion

    Longest ConsecutiveNot Completed

    Solutions: 311 | View all user solutions | Challenge discussion

    String ExpressionNot Completed

    Solutions: 143 | View all user solutions | Challenge discussion

    Charlie the DogNot Completed

    Solutions: 91 | View all user solutions | Challenge discussion

    Plus MinusNot Completed

    Solutions: 133 | View all user solutions | Challenge discussion

    PrimesNot Completed

    Solutions: 72 | View all user solutions | Challenge discussion

    String CalculateNot Completed

    Solutions: 35 | View all user solutions | Challenge discussion

    Hard Difficulty

    Sudoku Quadrant CheckerNot Completed

    Solutions: 141 | View all user solutions | Challenge discussion

    Optimal AssignmentsNot Completed

    Solutions: 539 | View all user solutions | Challenge discussion

    Transitivity RelationsNot Completed

    Solutions: 419 | View all user solutions | Challenge discussion

    Shortest PathNot Completed

    Solutions: 1200 | View all user solutions | Challenge discussion

    Polynomial ExpansionNot Completed

    Solutions: 304 | View all user solutions | Challenge discussion

    CalculatorNot Completed

    Solutions: 1188 | View all user solutions | Challenge discussion

    Pattern ChaserNot Completed

    Solutions: 780 | View all user solutions | Challenge discussion

    Weighted PathNot Completed

    Solutions: 367 | View all user solutions | Challenge discussion

    RREF MatrixNot Completed

    Solutions: 134 | View all user solutions | Challenge discussion

    Intersecting LinesNot Completed

    Solutions: 582 | View all user solutions | Challenge discussion

    Kaprekars ConstantNot Completed

    Solutions: 6241 | View all user solutions | Challenge discussion

    Hamiltonian PathNot Completed

    Solutions: 151 | View all user solutions | Challenge discussion

    Step WalkingNot Completed

    Solutions: 118 | View all user solutions | Challenge discussion

    Gas StationNot Completed

    Solutions: 601 | View all user solutions | Challenge discussion

    Symmetric MatrixNot Completed

    Solutions: 416 | View all user solutions | Challenge discussion

    Switch SortNot Completed

    Solutions: 293 | View all user solutions | Challenge discussion

    Matrix DeterminantNot Completed

    Solutions: 272 | View all user solutions | Challenge discussion

    Queen CheckNot Completed

    Solutions: 482 | View all user solutions | Challenge discussion

    Noughts DeterminerNot Completed

    Solutions: 384 | View all user solutions | Challenge discussion

    Blackjack HighestNot Completed

    Solutions: 554 | View all user solutions | Challenge discussion

    Alphabet Run EncryptionNot Completed

    Solutions: 249 | View all user solutions | Challenge discussion

    Vertex CoveringNot Completed

    Solutions: 148 | View all user solutions | Challenge discussion

    Knight JumpsNot Completed

    Solutions: 528 | View all user solutions | Challenge discussion

    Farthest NodesNot Completed

    Solutions: 157 | View all user solutions | Challenge discussion

    Line OrderingNot Completed

    Solutions: 74 | View all user solutions | Challenge discussion

    Quick KnightNot Completed

    Solutions: 69 | View all user solutions | Challenge discussion

    Square FiguresNot Completed

    Solutions: 161 | View all user solutions | Challenge discussion

    Connect Four WinnerNot Completed

    Solutions: 110 | View all user solutions | Challenge discussion

    Array JumpingNot Completed

    Solutions: 87 | View all user solutions | Challenge discussion

    Matrix BorderNot Completed

    Solutions: 83 | View all user solutions | Challenge discussion

    Roman Numeral ReductionNot Completed

    Solutions: 107 | View all user solutions | Challenge discussion

    Parallel SumsNot Completed

    Solutions: 169 | View all user solutions | Challenge discussion

    LCSNot Completed

    Solutions: 99 | View all user solutions | Challenge discussion

    Nim WinnerNot Completed

    Solutions: 60 | View all user solutions | Challenge discussion

    Pascals TriangleNot Completed

    Solutions: 119 | View all user solutions | Challenge discussion

    Reverse Polish NotationNot Completed

    Solutions: 225 | View all user solutions | Challenge discussion

    Max Heap CheckerNot Completed

    Solutions: 108 | View all user solutions | Challenge discussion

    Chessboard TravelingNot Completed

    Solutions: 2715 | View all user solutions | Challenge discussion

    Matching CouplesNot Completed

    Solutions: 127 | View all user solutions | Challenge discussion

    Approaching FibonacciNot Completed

    Solutions: 152 | View all user solutions | Challenge discussion

    Simple SATNot Completed

    Solutions: 81 | View all user solutions | Challenge discussion

    Array CouplesNot Completed

    Solutions: 121 | View all user solutions | Challenge discussion

    Bracket CombinationsNot Completed

    Solutions: 142 | View all user solutions | Challenge discussion

    Counting AnagramsNot Completed

    Solutions: 181 | View all user solutions | Challenge discussion

    Array RotationNot Completed

    Solutions: 200 | View all user solutions | Challenge discussion

    Maximal SquareNot Completed

    Solutions: 1894 | View all user solutions | Challenge discussion

    Maximal RectangleNot Completed

    Solutions: 49 | View all user solutions | Challenge discussion

    Bipartite MatchingNot Completed

    Solutions: 48 | View all user solutions | Challenge discussion

    Pentagonal NumberNot Completed

    Solutions: 1992 | View all user solutions | Challenge discussion

    City TrafficNot Completed

    Solutions: 51 | View all user solutions | Challenge discussion

    Convex Hull PointsNot Completed

    Solutions: 33 | View all user solutions | Challenge discussion

    Wildcard CharactersNot Completed

    Solutions: 84 | View all user solutions | Challenge discussion

    Tetris MoveNot Completed

    Solutions: 41 | View all user solutions | Challenge discussion

    WildcardsNot Completed

    Solutions: 36 | View all user solutions | Challenge discussion

    Difficulty

    Companies

    • Google 44
    • Facebook 23
    • Microsoft 21
    • Amazon 12

    Bootcamps

    • Hack Reactor 87
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    • Grace Hopper 87
    • App Academy 87
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    All Tags

    • searching 102
    • array 71
    • string manipulation 64
    • math fundamentals 58
    • hash table 23
    • optimization 22
    • matrix 21
    • dynamic programming 20
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    • game 10
    • algebra 10
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    • combinatorics 9
    • sorting 8
    • sequences 7
    • stack 7
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    • chess 5
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    • geometry 4
    • linear algebra 4
    • prime numbers 4
    • set theory 3
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    • cache 1