← Back to Citadel

Array

134 questions

1Sliding Window MaximumHard
ArrayQueueSliding Window
Solve →
2Merge IntervalsMedium
ArraySorting
Solve →
3Meeting SchedulerMedium
ArrayTwo PointersSorting
Solve →
4Find Servers That Handled Most Number of RequestsHard
ArrayGreedyHeap (Priority Queue)
Solve →
5Best Time to Buy and Sell StockEasy
ArrayDynamic Programming
Solve →
6Sliding Window MaximumHard
ArrayQueueSliding Window
Solve →
7Merge IntervalsMedium
ArraySorting
Solve →
8Evaluate DivisionMedium
ArrayStringDepth-First Search
Solve →
9Meeting SchedulerMedium
ArrayTwo PointersSorting
Solve →
10Employee Free TimeHard
ArrayLine SweepSorting
Solve →
11Parallel Courses IIIHard
ArrayDynamic ProgrammingGraph
Solve →
12Find the Duplicate NumberMedium
ArrayTwo PointersBinary Search
Solve →
13Insert Delete GetRandom O(1)Medium
ArrayHash TableMath
Solve →
14Number of IslandsMedium
ArrayDepth-First SearchBreadth-First Search
Solve →
15Find Servers That Handled Most Number of RequestsHard
ArrayGreedyHeap (Priority Queue)
Solve →
16Best Time to Buy and Sell StockEasy
ArrayDynamic Programming
Solve →
17Longest Non-decreasing Subarray From Two ArraysMedium
ArrayDynamic Programming
Solve →
18Delete and EarnMedium
ArrayHash TableDynamic Programming
Solve →
19Minimum Equal Sum of Two Arrays After Replacing ZerosMedium
ArrayGreedy
Solve →
20Minimum Operations to Make Numbers Non-positiveHard
ArrayBinary Search
Solve →
21Longest String ChainMedium
ArrayHash TableTwo Pointers
Solve →
22Evaluate Reverse Polish NotationMedium
ArrayMathStack
Solve →
23Sliding Window MaximumHard
ArrayQueueSliding Window
Solve →
24Best Time to Buy and Sell StockEasy
ArrayDynamic Programming
Solve →
25Insert Delete GetRandom O(1)Medium
ArrayHash TableMath
Solve →
26Length of Longest Subarray With at Most K FrequencyMedium
ArrayHash TableSliding Window
Solve →
27Evaluate DivisionMedium
ArrayStringDepth-First Search
Solve →
28Find the Duplicate NumberMedium
ArrayTwo PointersBinary Search
Solve →
29Group AnagramsMedium
ArrayHash TableString
Solve →
30Sudoku SolverHard
ArrayHash TableBacktracking
Solve →
31PermutationsMedium
ArrayBacktracking
Solve →
32Search Suggestions SystemMedium
ArrayStringBinary Search
Solve →
33Number of IslandsMedium
ArrayDepth-First SearchBreadth-First Search
Solve →
34Trapping Rain WaterHard
ArrayTwo PointersDynamic Programming
Solve →
35N-QueensHard
ArrayBacktracking
Solve →
36Maximum Total Damage With Spell CastingMedium
ArrayHash TableTwo Pointers
Solve →
37Best Time to Buy and Sell Stock IIMedium
ArrayDynamic ProgrammingGreedy
Solve →
38Design Circular QueueMedium
ArrayLinked ListDesign
Solve →
39Best Position for a Service CentreHard
ArrayMathGeometry
Solve →
40Design Excel Sum FormulaHard
ArrayHash TableString
Solve →
41Parallel Courses IIIHard
ArrayDynamic ProgrammingGraph
Solve →
42Maximum Length of Repeated SubarrayMedium
ArrayBinary SearchDynamic Programming
Solve →
43Combination SumMedium
ArrayBacktracking
Solve →
44Median of Two Sorted ArraysHard
ArrayBinary SearchDivide and Conquer
Solve →
45Maximal SquareMedium
ArrayDynamic ProgrammingMatrix
Solve →
46Alien DictionaryHard
ArrayStringDepth-First Search
Solve →
47Longest Increasing Path in a MatrixHard
ArrayDynamic ProgrammingDepth-First Search
Solve →
48Minimum Costs Using the Train LineHard
ArrayDynamic Programming
Solve →
49Best Time to Buy and Sell Stock IIIHard
ArrayDynamic Programming
Solve →
50House RobberMedium
ArrayDynamic Programming
Solve →
51Transform to ChessboardHard
ArrayMathBit Manipulation
Solve →
523SumMedium
ArrayTwo PointersSorting
Solve →
53Asteroid CollisionMedium
ArrayStackSimulation
Solve →
54Insert Delete GetRandom O(1) - Duplicates allowedHard
ArrayHash TableMath
Solve →
55Count Number of Maximum Bitwise-OR SubsetsMedium
ArrayBacktrackingBit Manipulation
Solve →
56Search a 2D Matrix IIMedium
ArrayBinary SearchDivide and Conquer
Solve →
57Design Front Middle Back QueueMedium
ArrayLinked ListDesign
Solve →
58Container With Most WaterMedium
ArrayTwo PointersGreedy
Solve →
59Paint HouseMedium
ArrayDynamic Programming
Solve →
60Max Points on a LineHard
ArrayHash TableMath
Solve →
61Rank Transform of a MatrixHard
ArrayUnion FindGraph
Solve →
62Longest Increasing SubsequenceMedium
ArrayBinary SearchDynamic Programming
Solve →
63Merge IntervalsMedium
ArraySorting
Solve →
64Rotting OrangesMedium
ArrayBreadth-First SearchMatrix
Solve →
65First Completely Painted Row or ColumnMedium
ArrayHash TableMatrix
Solve →
66The Skyline ProblemHard
ArrayDivide and ConquerBinary Indexed Tree
Solve →
67Permutations IIMedium
ArrayBacktrackingSorting
Solve →
68Subarray Sums Divisible by KMedium
ArrayHash TablePrefix Sum
Solve →
69Bus RoutesHard
ArrayHash TableBreadth-First Search
Solve →
70Best Time to Buy and Sell Stock IVHard
ArrayDynamic Programming
Solve →
71Word SearchMedium
ArrayStringBacktracking
Solve →
72Moving Average from Data StreamEasy
ArrayDesignQueue
Solve →
73Longest Non-decreasing Subarray From Two ArraysMedium
ArrayDynamic Programming
Solve →
74Delete and EarnMedium
ArrayHash TableDynamic Programming
Solve →
75Sliding Window MaximumHard
ArrayQueueSliding Window
Solve →
76Minimum Equal Sum of Two Arrays After Replacing ZerosMedium
ArrayGreedy
Solve →
77Minimum Operations to Make Numbers Non-positiveHard
ArrayBinary Search
Solve →
78Maximum Total Damage With Spell CastingMedium
ArrayHash TableTwo Pointers
Solve →
79Maximum Length of Repeated SubarrayMedium
ArrayBinary SearchDynamic Programming
Solve →
80Minimum Costs Using the Train LineHard
ArrayDynamic Programming
Solve →
81Best Position for a Service CentreHard
ArrayMathGeometry
Solve →
82Evaluate DivisionMedium
ArrayStringDepth-First Search
Solve →
83First Completely Painted Row or ColumnMedium
ArrayHash TableMatrix
Solve →
84Longest String ChainMedium
ArrayHash TableTwo Pointers
Solve →
85Merge IntervalsMedium
ArraySorting
Solve →
86Best Time to Buy and Sell StockEasy
ArrayDynamic Programming
Solve →
87Find the Duplicate NumberMedium
ArrayTwo PointersBinary Search
Solve →
88Evaluate Reverse Polish NotationMedium
ArrayMathStack
Solve →
89Insert Delete GetRandom O(1)Medium
ArrayHash TableMath
Solve →
90Sudoku SolverHard
ArrayHash TableBacktracking
Solve →
91Length of Longest Subarray With at Most K FrequencyMedium
ArrayHash TableSliding Window
Solve →
92Parallel Courses IIIHard
ArrayDynamic ProgrammingGraph
Solve →
93Number of IslandsMedium
ArrayDepth-First SearchBreadth-First Search
Solve →
94Group AnagramsMedium
ArrayHash TableString
Solve →
95Meeting SchedulerMedium
ArrayTwo PointersSorting
Solve →
96Employee Free TimeHard
ArrayLine SweepSorting
Solve →
97PermutationsMedium
ArrayBacktracking
Solve →
98N-QueensHard
ArrayBacktracking
Solve →
99Best Time to Buy and Sell Stock IIMedium
ArrayDynamic ProgrammingGreedy
Solve →
100Best Time to Buy and Sell Stock IIIHard
ArrayDynamic Programming
Solve →
101Search Suggestions SystemMedium
ArrayStringBinary Search
Solve →
102Combination SumMedium
ArrayBacktracking
Solve →
103Design Circular QueueMedium
ArrayLinked ListDesign
Solve →
104Trapping Rain WaterHard
ArrayTwo PointersDynamic Programming
Solve →
105Word SearchMedium
ArrayStringBacktracking
Solve →
106Design Excel Sum FormulaHard
ArrayHash TableString
Solve →
107Moving Average from Data StreamEasy
ArrayDesignQueue
Solve →
108Design Front Middle Back QueueMedium
ArrayLinked ListDesign
Solve →
109Median of Two Sorted ArraysHard
ArrayBinary SearchDivide and Conquer
Solve →
110Find Servers That Handled Most Number of RequestsHard
ArrayGreedyHeap (Priority Queue)
Solve →
111Longest Increasing Path in a MatrixHard
ArrayDynamic ProgrammingDepth-First Search
Solve →
112House RobberMedium
ArrayDynamic Programming
Solve →
113Maximal SquareMedium
ArrayDynamic ProgrammingMatrix
Solve →
1143SumMedium
ArrayTwo PointersSorting
Solve →
115Alien DictionaryHard
ArrayStringDepth-First Search
Solve →
116Transform to ChessboardHard
ArrayMathBit Manipulation
Solve →
117Best Time to Buy and Sell Stock with Transaction FeeMedium
ArrayDynamic ProgrammingGreedy
Solve →
118Open the LockMedium
ArrayHash TableString
Solve →
119Koko Eating BananasMedium
ArrayBinary Search
Solve →
120Max Points on a LineHard
ArrayHash TableMath
Solve →
121Permutations IIMedium
ArrayBacktrackingSorting
Solve →
122Container With Most WaterMedium
ArrayTwo PointersGreedy
Solve →
123Rotting OrangesMedium
ArrayBreadth-First SearchMatrix
Solve →
124Longest Increasing SubsequenceMedium
ArrayBinary SearchDynamic Programming
Solve →
125Rank Transform of a MatrixHard
ArrayUnion FindGraph
Solve →
126Paint HouseMedium
ArrayDynamic Programming
Solve →
127Subarray Sums Divisible by KMedium
ArrayHash TablePrefix Sum
Solve →
128Search a 2D Matrix IIMedium
ArrayBinary SearchDivide and Conquer
Solve →
129Best Time to Buy and Sell Stock IVHard
ArrayDynamic Programming
Solve →
130Insert Delete GetRandom O(1) - Duplicates allowedHard
ArrayHash TableMath
Solve →
131Bus RoutesHard
ArrayHash TableBreadth-First Search
Solve →
132Asteroid CollisionMedium
ArrayStackSimulation
Solve →
133The Skyline ProblemHard
ArrayDivide and ConquerBinary Indexed Tree
Solve →
134Count Number of Maximum Bitwise-OR SubsetsMedium
ArrayBacktrackingBit Manipulation
Solve →