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    Group TotalsNot Completed

    Solutions: 109 | View user solutions | Added 04/30/18

    Moving MedianNot Completed

    Solutions: 157 | View user solutions | Added 11/30/17

    Star RatingNot Completed

    Solutions: 383 | View user solutions | Added 10/30/17

    Free Challenges

    Longest WordNot Completed

    Solutions: 69052 | Step-by-step solution | Challenge discussion

    First FactorialNot Completed

    Solutions: 87132 | Step-by-step solution | Challenge discussion

    First ReverseNot Completed

    Solutions: 109456 | Step-by-step solution | Challenge discussion

    Letter ChangesNot Completed

    Solutions: 66526 | Step-by-step solution | Challenge discussion

    Simple AddingNot Completed

    Solutions: 54447 | Step-by-step solution | Challenge discussion

    Letter CapitalizeNot Completed

    Solutions: 46338 | Step-by-step solution | Challenge discussion

    Simple SymbolsNot Completed

    Solutions: 39408 | Step-by-step solution | Challenge discussion

    Check NumsNot Completed

    Solutions: 39921 | Step-by-step solution | Challenge discussion

    Time ConvertNot Completed

    Solutions: 30285 | Step-by-step solution | Challenge discussion

    Alphabet SoupNot Completed

    Solutions: 27995 | Step-by-step solution | Challenge discussion

    Kaprekars ConstantNot Completed

    Solutions: 3717 | View all user solutions | Challenge discussion

    Chessboard TravelingNot Completed

    Solutions: 1541 | View all user solutions | Challenge discussion

    Maximal SquareNot Completed

    Solutions: 989 | View all user solutions | Challenge discussion

    Pentagonal NumberNot Completed

    Solutions: 1065 | View all user solutions | Challenge discussion

    Correct PathNot Completed

    Solutions: 1328 | View all user solutions | Challenge discussion

    Scale BalancingNot Completed

    Solutions: 1778 | View all user solutions | Challenge discussion

    Vowel SquareNot Completed

    Solutions: 1174 | View all user solutions | Challenge discussion

    Eight QueensNot Completed

    Solutions: 794 | View all user solutions | Challenge discussion

    Closest Enemy IINot Completed

    Solutions: 1006 | View all user solutions | Challenge discussion

    Questions MarksNot Completed

    Solutions: 2929 | View all user solutions | Challenge discussion

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    Easy Difficulty

    First ReverseNot Completed

    Solutions: 109456 | Step-by-step solution | Challenge discussion

    First FactorialNot Completed

    Solutions: 87132 | Step-by-step solution | Challenge discussion

    Longest WordNot Completed

    Solutions: 69052 | Step-by-step solution | Challenge discussion

    Letter ChangesNot Completed

    Solutions: 66526 | Step-by-step solution | Challenge discussion

    Simple AddingNot Completed

    Solutions: 54447 | Step-by-step solution | Challenge discussion

    Letter CapitalizeNot Completed

    Solutions: 46338 | Step-by-step solution | Challenge discussion

    Simple SymbolsNot Completed

    Solutions: 39408 | Step-by-step solution | Challenge discussion

    Check NumsNot Completed

    Solutions: 39921 | Step-by-step solution | Challenge discussion

    Time ConvertNot Completed

    Solutions: 30285 | Step-by-step solution | Challenge discussion

    Alphabet SoupNot Completed

    Solutions: 27995 | Step-by-step solution | Challenge discussion

    AB CheckNot Completed

    Solutions: 16795 | Step-by-step solution | Challenge discussion

    Vowel CountNot Completed

    Solutions: 15463 | Step-by-step solution | Challenge discussion

    Word CountNot Completed

    Solutions: 14608 | Step-by-step solution | Challenge discussion

    Ex OhNot Completed

    Solutions: 14282 | Step-by-step solution | Challenge discussion

    PalindromeNot Completed

    Solutions: 16641 | Step-by-step solution | Challenge discussion

    Arith GeoNot Completed

    Solutions: 13261 | Step-by-step solution | Challenge discussion

    Array Addition INot Completed

    Solutions: 8473 | Step-by-step solution | Challenge discussion

    Letter Count INot Completed

    Solutions: 7772 | Step-by-step solution | Challenge discussion

    Second GreatLowNot Completed

    Solutions: 12894 | Step-by-step solution | Challenge discussion

    Division StringifiedNot Completed

    Solutions: 9681 | Step-by-step solution | Challenge discussion

    Counting Minutes INot Completed

    Solutions: 5727 | Step-by-step solution | Challenge discussion

    Mean ModeNot Completed

    Solutions: 7524 | Step-by-step solution | Challenge discussion

    Dash InsertNot Completed

    Solutions: 8522 | Step-by-step solution | Challenge discussion

    Swap CaseNot Completed

    Solutions: 8078 | Step-by-step solution | Challenge discussion

    Number AdditionNot Completed

    Solutions: 7938 | Step-by-step solution | Challenge discussion

    Third GreatestNot Completed

    Solutions: 7339 | Step-by-step solution | Challenge discussion

    Powers of TwoNot Completed

    Solutions: 8227 | Step-by-step solution | Challenge discussion

    Additive PersistenceNot Completed

    Solutions: 5858 | Step-by-step solution | Challenge discussion

    Multiplicative PersistenceNot Completed

    Solutions: 4516 | Step-by-step solution | Challenge discussion

    Off Line MinimumNot Completed

    Solutions: 6069 | Step-by-step solution | Challenge discussion

    Changing SequenceNot Completed

    Solutions: 2493 | Step-by-step solution | Challenge discussion

    Overlapping RangesNot Completed

    Solutions: 2490 | Step-by-step solution | Challenge discussion

    SuperincreasingNot Completed

    Solutions: 2532 | Step-by-step solution | Challenge discussion

    Hamming DistanceNot Completed

    Solutions: 1728 | Step-by-step solution | Challenge discussion

    Rectangle AreaNot Completed

    Solutions: 2108 | Step-by-step solution | Challenge discussion

    Bitwise OneNot Completed

    Solutions: 1713 | Step-by-step solution | Challenge discussion

    Other ProductsNot Completed

    Solutions: 1744 | Step-by-step solution | Challenge discussion

    Wave SortingNot Completed

    Solutions: 1214 | Step-by-step solution | Challenge discussion

    Array MatchingNot Completed

    Solutions: 1489 | Step-by-step solution | Challenge discussion

    Binary ReversalNot Completed

    Solutions: 1232 | Step-by-step solution | Challenge discussion

    Longest Increasing SequenceNot Completed

    Solutions: 1179 | Step-by-step solution | Challenge discussion

    Even PairsNot Completed

    Solutions: 1128 | Step-by-step solution | Challenge discussion

    Next PalindromeNot Completed

    Solutions: 986 | Step-by-step solution | Challenge discussion

    Largest PairNot Completed

    Solutions: 1319 | Step-by-step solution | Challenge discussion

    Nonrepeating CharacterNot Completed

    Solutions: 973 | Step-by-step solution | Challenge discussion

    Two SumNot Completed

    Solutions: 1780 | Step-by-step solution | Challenge discussion

    Bitwise TwoNot Completed

    Solutions: 701 | Step-by-step solution | Challenge discussion

    Power Set CountNot Completed

    Solutions: 1030 | Step-by-step solution | Challenge discussion

    Product DigitsNot Completed

    Solutions: 1297 | Step-by-step solution | Challenge discussion

    Palindrome CreatorNot Completed

    Solutions: 1063 | Step-by-step solution | Challenge discussion

    Basic Roman NumeralsNot Completed

    Solutions: 713 | Step-by-step solution | Challenge discussion

    Food DistributionNot Completed

    Solutions: 614 | Step-by-step solution | Challenge discussion

    Three SumNot Completed

    Solutions: 718 | Step-by-step solution | Challenge discussion

    Correct PathNot Completed

    Solutions: 1328 | Step-by-step solution | Challenge discussion

    Scale BalancingNot Completed

    Solutions: 1778 | Step-by-step solution | Challenge discussion

    Three NumbersNot Completed

    Solutions: 682 | Step-by-step solution | Challenge discussion

    Alphabet SearchingNot Completed

    Solutions: 581 | Step-by-step solution | Challenge discussion

    Time DifferenceNot Completed

    Solutions: 377 | Step-by-step solution | Challenge discussion

    Triangle RowNot Completed

    Solutions: 367 | Step-by-step solution | Challenge discussion

    Vowel SquareNot Completed

    Solutions: 1174 | Step-by-step solution | Challenge discussion

    Closest EnemyNot Completed

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

    Closest Enemy IINot Completed

    Solutions: 1006 | Step-by-step solution | Challenge discussion

    Number StreamNot Completed

    Solutions: 362 | Step-by-step solution | Challenge discussion

    Largest FourNot Completed

    Solutions: 538 | Step-by-step solution | Challenge discussion

    Distinct CharactersNot Completed

    Solutions: 385 | Step-by-step solution | Challenge discussion

    Questions MarksNot Completed

    Solutions: 2929 | Step-by-step solution | Challenge discussion

    Camel CaseNot Completed

    Solutions: 454 | Step-by-step solution | Challenge discussion

    ASCII ConversionNot Completed

    Solutions: 311 | Step-by-step solution | Challenge discussion

    Simple EvensNot Completed

    Solutions: 427 | Step-by-step solution | Challenge discussion

    Snake CaseNot Completed

    Solutions: 372 | Step-by-step solution | Challenge discussion

    Sum MultiplierNot Completed

    Solutions: 468 | Step-by-step solution | Challenge discussion

    String MergeNot Completed

    Solutions: 440 | Step-by-step solution | Challenge discussion

    One DecrementedNot Completed

    Solutions: 414 | Step-by-step solution | Challenge discussion

    Element MergerNot Completed

    Solutions: 444 | Step-by-step solution | Challenge discussion

    GCFNot Completed

    Solutions: 410 | Step-by-step solution | Challenge discussion

    Serial NumberNot Completed

    Solutions: 567 | Step-by-step solution | Challenge discussion

    String PeriodsNot Completed

    Solutions: 488 | Step-by-step solution | Challenge discussion

    Palindrome SwapperNot Completed

    Solutions: 288 | Step-by-step solution | Challenge discussion

    Remove BracketsNot Completed

    Solutions: 414 | Step-by-step solution | Challenge discussion

    Command LineNot Completed

    Solutions: 185 | Step-by-step solution | Challenge discussion

    Star RatingNot Completed

    Solutions: 383 | Step-by-step solution | Challenge discussion

    Moving MedianNot Completed

    Solutions: 157 | Step-by-step solution | Challenge discussion

    Group TotalsNot Completed

    Solutions: 109 | Step-by-step solution | Challenge discussion

    Medium Difficulty

    Prime TimeNot Completed

    Solutions: 11979 | Step-by-step solution | Challenge discussion

    Run Length Not Completed

    Solutions: 8524 | Step-by-step solution | Challenge discussion

    Prime MoverNot Completed

    Solutions: 7416 | Step-by-step solution | Challenge discussion

    Palindrome TwoNot Completed

    Solutions: 7086 | Step-by-step solution | Challenge discussion

    DivisionNot Completed

    Solutions: 6603 | Step-by-step solution | Challenge discussion

    String ScrambleNot Completed

    Solutions: 7222 | Step-by-step solution | Challenge discussion

    Arith Geo IINot Completed

    Solutions: 4974 | Step-by-step solution | Challenge discussion

    Array AdditionNot Completed

    Solutions: 4364 | Step-by-step solution | Challenge discussion

    Binary ConverterNot Completed

    Solutions: 4501 | Step-by-step solution | Challenge discussion

    Letter CountNot Completed

    Solutions: 4455 | Step-by-step solution | Challenge discussion

    Caesar CipherNot Completed

    Solutions: 5113 | Step-by-step solution | Challenge discussion

    Simple ModeNot Completed

    Solutions: 4986 | Step-by-step solution | Challenge discussion

    ConsecutiveNot Completed

    Solutions: 4087 | Step-by-step solution | Challenge discussion

    Formatted DivisionNot Completed

    Solutions: 3774 | Step-by-step solution | Challenge discussion

    Counting MinutesNot Completed

    Solutions: 2775 | View all user solutions | Challenge discussion

    Permutation StepNot Completed

    Solutions: 3288 | View all user solutions | Challenge discussion

    Prime CheckerNot Completed

    Solutions: 2530 | View all user solutions | Challenge discussion

    Dash Insert IINot Completed

    Solutions: 4894 | View all user solutions | Challenge discussion

    Swap IINot Completed

    Solutions: 2722 | View all user solutions | Challenge discussion

    Number SearchNot Completed

    Solutions: 3337 | View all user solutions | Challenge discussion

    Triple DoubleNot Completed

    Solutions: 3107 | View all user solutions | Challenge discussion

    Bracket MatcherNot Completed

    Solutions: 2825 | View all user solutions | Challenge discussion

    String ReductionNot Completed

    Solutions: 2331 | View all user solutions | Challenge discussion

    ThreeFive MultiplesNot Completed

    Solutions: 2823 | View all user solutions | Challenge discussion

    Binary Search Tree LCANot Completed

    Solutions: 251 | View all user solutions | Challenge discussion

    Coin DeterminerNot Completed

    Solutions: 2289 | View all user solutions | Challenge discussion

    Fibonacci CheckerNot Completed

    Solutions: 2640 | View all user solutions | Challenge discussion

    Multiple BracketsNot Completed

    Solutions: 2335 | View all user solutions | Challenge discussion

    Most Free TimeNot Completed

    Solutions: 1410 | View all user solutions | Challenge discussion

    Overlapping RectanglesNot Completed

    Solutions: 1612 | View all user solutions | Challenge discussion

    Look Say SequenceNot Completed

    Solutions: 1466 | View all user solutions | Challenge discussion

    Distinct ListNot Completed

    Solutions: 2393 | View all user solutions | Challenge discussion

    Number EncodingNot Completed

    Solutions: 1485 | View all user solutions | Challenge discussion

    Stock PickerNot Completed

    Solutions: 732 | View all user solutions | Challenge discussion

    Max SubarrayNot Completed

    Solutions: 645 | View all user solutions | Challenge discussion

    Missing DigitNot Completed

    Solutions: 446 | View all user solutions | Challenge discussion

    K Unique CharactersNot Completed

    Solutions: 439 | View all user solutions | Challenge discussion

    Bitmap HolesNot Completed

    Solutions: 320 | View all user solutions | Challenge discussion

    Symmetric TreeNot Completed

    Solutions: 281 | View all user solutions | Challenge discussion

    Binary Tree LCANot Completed

    Solutions: 146 | View all user solutions | Challenge discussion

    LRU CacheNot Completed

    Solutions: 184 | View all user solutions | Challenge discussion

    Tree ConstructorNot Completed

    Solutions: 292 | View all user solutions | Challenge discussion

    Array Min JumpsNot Completed

    Solutions: 221 | View all user solutions | Challenge discussion

    Nearest Smaller ValuesNot Completed

    Solutions: 392 | View all user solutions | Challenge discussion

    Matrix SpiralNot Completed

    Solutions: 192 | View all user solutions | Challenge discussion

    Word SplitNot Completed

    Solutions: 353 | View all user solutions | Challenge discussion

    Pair SearchingNot Completed

    Solutions: 120 | View all user solutions | Challenge discussion

    Boggle SolverNot Completed

    Solutions: 91 | View all user solutions | Challenge discussion

    HTML ElementsNot Completed

    Solutions: 151 | View all user solutions | Challenge discussion

    Missing Digit IINot Completed

    Solutions: 149 | View all user solutions | Challenge discussion

    Palindromic SubstringNot Completed

    Solutions: 256 | View all user solutions | Challenge discussion

    Trapping WaterNot Completed

    Solutions: 150 | View all user solutions | Challenge discussion

    Matrix PathNot Completed

    Solutions: 76 | View all user solutions | Challenge discussion

    Seating StudentsNot Completed

    Solutions: 148 | View all user solutions | Challenge discussion

    Longest Matrix PathNot Completed

    Solutions: 65 | View all user solutions | Challenge discussion

    Min Window SubstringNot Completed

    Solutions: 148 | View all user solutions | Challenge discussion

    Matrix ChainsNot Completed

    Solutions: 66 | View all user solutions | Challenge discussion

    Histogram AreaNot Completed

    Solutions: 116 | View all user solutions | Challenge discussion

    Matching CharactersNot Completed

    Solutions: 161 | View all user solutions | Challenge discussion

    Ternary ConverterNot Completed

    Solutions: 90 | View all user solutions | Challenge discussion

    Linear CongruenceNot Completed

    Solutions: 52 | View all user solutions | Challenge discussion

    Formatted NumberNot Completed

    Solutions: 189 | View all user solutions | Challenge discussion

    Largest Row ColumnNot Completed

    Solutions: 54 | View all user solutions | Challenge discussion

    Eight QueensNot Completed

    Solutions: 794 | View all user solutions | Challenge discussion

    Three PointsNot Completed

    Solutions: 123 | View all user solutions | Challenge discussion

    Character RemovalNot Completed

    Solutions: 137 | View all user solutions | Challenge discussion

    Simple PasswordNot Completed

    Solutions: 188 | View all user solutions | Challenge discussion

    Preorder TraversalNot Completed

    Solutions: 86 | View all user solutions | Challenge discussion

    String ZigzagNot Completed

    Solutions: 92 | View all user solutions | Challenge discussion

    Off BinaryNot Completed

    Solutions: 81 | View all user solutions | Challenge discussion

    Longest ConsecutiveNot Completed

    Solutions: 287 | View all user solutions | Challenge discussion

    String ExpressionNot Completed

    Solutions: 132 | View all user solutions | Challenge discussion

    Charlie the DogNot Completed

    Solutions: 69 | View all user solutions | Challenge discussion

    Plus MinusNot Completed

    Solutions: 112 | View all user solutions | Challenge discussion

    Hard Difficulty

    Sudoku Quadrant CheckerNot Completed

    Solutions: 113 | View all user solutions | Challenge discussion

    Optimal AssignmentsNot Completed

    Solutions: 511 | View all user solutions | Challenge discussion

    Transitivity RelationsNot Completed

    Solutions: 413 | View all user solutions | Challenge discussion

    Shortest PathNot Completed

    Solutions: 1153 | View all user solutions | Challenge discussion

    Polynomial ExpansionNot Completed

    Solutions: 289 | View all user solutions | Challenge discussion

    CalculatorNot Completed

    Solutions: 1159 | View all user solutions | Challenge discussion

    Pattern ChaserNot Completed

    Solutions: 755 | View all user solutions | Challenge discussion

    Weighted PathNot Completed

    Solutions: 360 | View all user solutions | Challenge discussion

    RREF MatrixNot Completed

    Solutions: 123 | View all user solutions | Challenge discussion

    Intersecting LinesNot Completed

    Solutions: 564 | View all user solutions | Challenge discussion

    Kaprekars ConstantNot Completed

    Solutions: 3717 | View all user solutions | Challenge discussion

    Hamiltonian PathNot Completed

    Solutions: 140 | View all user solutions | Challenge discussion

    Step WalkingNot Completed

    Solutions: 104 | View all user solutions | Challenge discussion

    Gas StationNot Completed

    Solutions: 578 | View all user solutions | Challenge discussion

    Symmetric MatrixNot Completed

    Solutions: 405 | View all user solutions | Challenge discussion

    Switch SortNot Completed

    Solutions: 282 | View all user solutions | Challenge discussion

    Matrix DeterminantNot Completed

    Solutions: 265 | View all user solutions | Challenge discussion

    Queen CheckNot Completed

    Solutions: 466 | View all user solutions | Challenge discussion

    Noughts DeterminerNot Completed

    Solutions: 379 | View all user solutions | Challenge discussion

    Blackjack HighestNot Completed

    Solutions: 521 | View all user solutions | Challenge discussion

    Alphabet Run EncryptionNot Completed

    Solutions: 245 | View all user solutions | Challenge discussion

    Vertex CoveringNot Completed

    Solutions: 138 | View all user solutions | Challenge discussion

    Knight JumpsNot Completed

    Solutions: 522 | View all user solutions | Challenge discussion

    Farthest NodesNot Completed

    Solutions: 150 | View all user solutions | Challenge discussion

    Line OrderingNot Completed

    Solutions: 64 | View all user solutions | Challenge discussion

    Quick KnightNot Completed

    Solutions: 58 | View all user solutions | Challenge discussion

    Square FiguresNot Completed

    Solutions: 147 | View all user solutions | Challenge discussion

    Connect Four WinnerNot Completed

    Solutions: 107 | View all user solutions | Challenge discussion

    Array JumpingNot Completed

    Solutions: 78 | View all user solutions | Challenge discussion

    Matrix BorderNot Completed

    Solutions: 65 | View all user solutions | Challenge discussion

    Roman Numeral ReductionNot Completed

    Solutions: 92 | View all user solutions | Challenge discussion

    Parallel SumsNot Completed

    Solutions: 146 | View all user solutions | Challenge discussion

    LCSNot Completed

    Solutions: 86 | View all user solutions | Challenge discussion

    Nim WinnerNot Completed

    Solutions: 51 | View all user solutions | Challenge discussion

    Pascals TriangleNot Completed

    Solutions: 110 | View all user solutions | Challenge discussion

    Reverse Polish NotationNot Completed

    Solutions: 218 | View all user solutions | Challenge discussion

    Max Heap CheckerNot Completed

    Solutions: 102 | View all user solutions | Challenge discussion

    Chessboard TravelingNot Completed

    Solutions: 1541 | View all user solutions | Challenge discussion

    Matching CouplesNot Completed

    Solutions: 118 | View all user solutions | Challenge discussion

    Approaching FibonacciNot Completed

    Solutions: 138 | View all user solutions | Challenge discussion

    Simple SATNot Completed

    Solutions: 74 | View all user solutions | Challenge discussion

    Array CouplesNot Completed

    Solutions: 112 | View all user solutions | Challenge discussion

    Bracket CombinationsNot Completed

    Solutions: 130 | View all user solutions | Challenge discussion

    Counting AnagramsNot Completed

    Solutions: 163 | View all user solutions | Challenge discussion

    Array RotationNot Completed

    Solutions: 172 | View all user solutions | Challenge discussion

    Maximal SquareNot Completed

    Solutions: 989 | View all user solutions | Challenge discussion

    Maximal RectangleNot Completed

    Solutions: 42 | View all user solutions | Challenge discussion

    Bipartite MatchingNot Completed

    Solutions: 41 | View all user solutions | Challenge discussion

    Pentagonal NumberNot Completed

    Solutions: 1065 | View all user solutions | Challenge discussion

    City TrafficNot Completed

    Solutions: 42 | View all user solutions | Challenge discussion

    Convex Hull PointsNot Completed

    Solutions: 28 | View all user solutions | Challenge discussion

    Wildcard CharactersNot Completed

    Solutions: 78 | View all user solutions | Challenge discussion

    Tetris MoveNot Completed

    Solutions: 18 | View all user solutions | Challenge discussion

    Difficulty

    Companies

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    • Microsoft 20
    • Amazon 12

    Bootcamps

    • Hack Reactor 83
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    • Grace Hopper 83
    • App Academy 83
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    • searching 101
    • array 70
    • string manipulation 59
    • math fundamentals 55
    • hash table 23
    • optimization 22
    • matrix 21
    • dynamic programming 20
    • recursion 13
    • regular expression 10
    • game 10
    • graph 9
    • algebra 9
    • combinatorics 9
    • sorting 8
    • sequences 7
    • stack 7
    • encoding 6
    • chess 5
    • binary tree 5
    • geometry 4
    • linear algebra 4
    • prime numbers 3
    • set theory 3
    • heap 3
    • bitwise operation 2
    • cache 1