Practice · judged on hidden tests

Problems

100 problems, ordered so each topic builds on the last.

Not startedMerging many sorted lists at onceSorting, Arrays, HeapsHard
Not startedMirror the treeTreesEasy
Not startedMost frequent numbersHash maps, Sorting, ArraysMedium
Not startedMove the zeroes to the endArrays, Two pointersEasy
Not startedProduct of everything elsePrefix sums, ArraysMedium
Not startedRaising to a power without multiplying that many timesBasics, NumbersMedium
Not startedReading a tree one level at a timeTrees, Stacks and queuesMedium
Not startedReads the same backwardsBasics, NumbersEasy
Not startedRead the grid in a spiralArrays, MatricesMedium
Not startedRunning sumPrefix sums, ArraysEasy
Not startedSearch insert positionBinary search, ArraysEasy
Not startedSharing the books so nobody reads too muchBinary search, ArraysMedium
Not startedShortest stretch that reaches the targetArrays, Sliding windowMedium
Not startedSorting 0s, 1s and 2s in one passSorting, Arrays, Two pointersMedium
Not startedSqueeze out the duplicatesArrays, Two pointersEasy
Not startedThe best k days in a rowArrays, Sliding windowEasy
Not startedThe best you can take without touching neighboursDynamic programming, ArraysMedium
Not startedThe biggest rectangle inside a histogramArrays, Stacks and queuesHard
Not startedThe cheapest way down through the gridDynamic programming, Arrays, MatricesMedium
Not startedThe deepest node both of them are underTreesMedium
Not startedThe first letter that has appeared only once, so farHash maps, Stacks and queues, StringsMedium
Not startedThe first negative number in every windowArrays, Stacks and queues, Sliding windowMedium
Not startedThe kth largest, without sorting everythingArrays, HeapsMedium
Not startedThe kth smallest value in a search treeBinary search, TreesMedium
Not startedThe largest number in every windowArrays, Stacks and queues, Sliding windowHard