Curated collection / 100 problems

The Core 100.

Practice one hundred high-signal problems across the patterns that show up most. Use this collection for independent reps after learning the underlying pattern.

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Math · Easy

100 problems0 complete in this view

001Fizz BuzzMathEasy↗

002Two SumArrays & HashingEasy↗

003Valid AnagramArrays & HashingEasy↗

004Reverse StringTwo PointersEasy↗

005Valid PalindromeTwo PointersEasy↗

006Longest Common PrefixArrays & HashingEasy↗

007Power of ThreeMathEasy↗

008Number of 1 BitsBit ManipulationEasy↗

009Range Sum Query - ImmutableArrays & HashingEasy↗

010Fibonacci NumberDynamic ProgrammingEasy↗

011Climbing StairsDynamic ProgrammingEasy↗

012Min Cost Climbing StairsDynamic ProgrammingEasy↗

013Best Time to Buy and Sell StockDynamic ProgrammingEasy↗

014Binary Tree Inorder TraversalTreesEasy↗

015Invert Binary TreeTreesEasy↗

016Symmetric TreeTreesEasy↗

017Maximum Depth of Binary TreeTreesEasy↗

018Same TreeTreesEasy↗

019Path SumTreesEasy↗

020Minimum Depth of Binary TreeTreesEasy↗

021Validate Binary Search TreeTreesMedium↗

022Reverse Linked ListLinked ListEasy↗

023Middle of the Linked ListLinked ListEasy↗

024Binary Tree Level Order TraversalTreesMedium↗

025Find if Path Exists in GraphGraphsEasy↗

026Number of IslandsGraphsMedium↗

027Max Area of IslandGraphsMedium↗

028Count Sub IslandsGraphsMedium↗

029Valid ParenthesesStackEasy↗

030Product of Array Except SelfArrays & HashingMedium↗

031Binary SearchBinary SearchEasy↗

032Minimum Add to Make Parentheses ValidStackMedium↗

033Longest Palindromic SubstringDynamic ProgrammingMedium↗

034Two Sum II - Input Array Is SortedTwo PointersMedium↗

035Container With Most WaterTwo PointersMedium↗

0363SumTwo PointersMedium↗

037Group AnagramsArrays & HashingMedium↗

038Kth Largest Element in an ArrayHeapMedium↗

039K Closest Points to OriginHeapMedium↗

040Insert Delete GetRandom O(1)DesignMedium↗

041First Bad VersionBinary SearchEasy↗

042Find Peak ElementBinary SearchMedium↗

043Sqrt(x)Binary SearchEasy↗

044Koko Eating BananasBinary SearchMedium↗

045Subarray Sum Equals KArrays & HashingMedium↗

046Continuous Subarray SumArrays & HashingMedium↗

047Count Number of Nice SubarraysSliding WindowMedium↗

048Clone GraphGraphsMedium↗

049Copy List with Random PointerLinked ListMedium↗

050Is Graph BipartiteGraphsMedium↗

051Evaluate DivisionGraphsMedium↗

052Maximum SubarrayDynamic ProgrammingMedium↗

053Maximum Product SubarrayDynamic ProgrammingMedium↗

054Unique PathsDynamic ProgrammingMedium↗

055Minimum Path SumDynamic ProgrammingMedium↗

056Longest Substring Without Repeating CharactersSliding WindowMedium↗

057Max Consecutive Ones IIISliding WindowMedium↗

058Maximize the Confusion of An ExamSliding WindowMedium↗

059Longest Nice SubarraySliding WindowMedium↗

060Random Pick with WeightBinary SearchMedium↗

061Word BreakDynamic ProgrammingMedium↗

062House RobberDynamic ProgrammingMedium↗

063Coin ChangeDynamic ProgrammingMedium↗

064Longest Increasing SubsequenceDynamic ProgrammingMedium↗

065Longest Common SubsequenceDynamic ProgrammingMedium↗

066Lowest Common Ancestor of a Binary Search TreeTreesMedium↗

067Binary Tree Maximum Path SumTreesHard↗

068Best Time to Buy and Sell Stock IIDynamic ProgrammingMedium↗

069Jump GameGreedyMedium↗

070Course Schedule IIGraphsMedium↗

071Path with Maximum ProbabilityGraphsMedium↗

072Path With Minimum EffortGraphsMedium↗

073Merge IntervalsIntervalsMedium↗

074Insert IntervalIntervalsMedium↗

075Interval List IntersectionsIntervalsMedium↗

076LRU CacheDesignMedium↗

077Binary Search Tree IteratorTreesMedium↗

078Min StackStackMedium↗

079Implement Stack using QueuesStackEasy↗

080Letter Combinations of a Phone NumberBacktrackingMedium↗

081Combination SumBacktrackingMedium↗

082PermutationsBacktrackingMedium↗

083SubsetsBacktrackingMedium↗

084Palindrome PartitioningBacktrackingMedium↗

085Implement Trie (Prefix Tree)TrieMedium↗

086Basic CalculatorStackHard↗

087Daily TemperaturesStackMedium↗

088Online Stock SpanStackMedium↗

089Partition Equal Subset SumDynamic ProgrammingMedium↗

090Redundant ConnectionGraphsMedium↗

091Find Median from Data StreamHeapHard↗

092Trapping Rain WaterTwo PointersHard↗

093Max Points on a LineMathHard↗

094Serialize and Deserialize Binary TreeTreesHard↗

095Maximum Profit in Job SchedulingDynamic ProgrammingHard↗

096Sliding Window MaximumSliding WindowHard↗

097Edit DistanceDynamic ProgrammingHard↗

098Largest Rectangle in HistogramStackHard↗

099Number of AtomsStackHard↗

100LFU CacheDesignHard↗