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100 questions tracked100 with solutions
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Frequency scoreSorted highest β†’ lowest frequencyβœ“ Our Solution = we have a detailed walkthrough

Showing 100 of 100 questions

1
100
ArrayHash Table
2
MediumLongest Substring Without Repeating Charactersβœ“ Our Solution
76
Hash TableStringSliding Window
3
MediumContainer With Most Waterβœ“ Our Solution
74
ArrayTwo PointersGreedy
4
EasyRoman to Integerβœ“ Our Solution
73
Hash TableMathString
5
EasyMaximum Depth of Binary Treeβœ“ Our Solution
72
TreeDepth-First SearchBreadth-First SearchBinary Tree
6
HardMedian of Two Sorted Arraysβœ“ Our Solution
70
ArrayBinary SearchDivide and Conquer
7
EasyRemove Duplicates from Sorted Arrayβœ“ Our Solution
70
ArrayTwo Pointers
8
70
ArrayTwo PointersSorting
9
MediumAdd Two Numbersβœ“ Our Solution
69
Linked ListMathRecursion
10
EasyMerge Sorted Arrayβœ“ Our Solution
69
ArrayTwo PointersSorting
11
MediumLRU Cacheβœ“ Our Solution
68
Hash TableLinked ListDesignDoubly-Linked List
12
MediumLongest Palindromic Substringβœ“ Our Solution
68
Two PointersStringDynamic Programming
13
MediumRotate Imageβœ“ Our Solution
65
ArrayMathMatrix
14
MediumWord Breakβœ“ Our Solution
65
ArrayHash TableStringDynamic Programming+2
15
EasyBest Time to Buy and Sell Stockβœ“ Our Solution
65
ArrayDynamic Programming
16
EasyMerge Two Sorted Listsβœ“ Our Solution
63
Linked ListRecursion
17
EasyValid Parenthesesβœ“ Our Solution
63
StringStack
18
EasyLinked List Cycleβœ“ Our Solution
63
Hash TableLinked ListTwo Pointers
19
EasyClimbing Stairsβœ“ Our Solution
63
MathDynamic ProgrammingMemoization
20
EasyLongest Common Prefixβœ“ Our Solution
63
StringTrie
21
EasyPalindrome Numberβœ“ Our Solution
63
Math
22
MediumMerge Intervalsβœ“ Our Solution
61
ArraySorting
23
MediumGenerate Parenthesesβœ“ Our Solution
61
StringDynamic ProgrammingBacktracking
24
MediumJump Gameβœ“ Our Solution
59
ArrayDynamic ProgrammingGreedy
25
MediumSpiral Matrixβœ“ Our Solution
57
ArrayMatrixSimulation
26
MediumGroup Anagramsβœ“ Our Solution
54
ArrayHash TableStringSorting
27
HardTrapping Rain Waterβœ“ Our Solution
54
ArrayTwo PointersDynamic ProgrammingStack+1
28
EasySearch Insert Positionβœ“ Our Solution
54
ArrayBinary Search
29
EasyRemove Elementβœ“ Our Solution
54
ArrayTwo Pointers
30
MediumCombination Sumβœ“ Our Solution
52
ArrayBacktracking
31
52
ArrayMath
32
EasyFind the Index of the First Occurrence in a Stringβœ“ Our Solution
52
Two PointersStringString Matching
33
MediumCount and Sayβœ“ Our Solution
52
String
34
MediumReverse Integerβœ“ Our Solution
52
Math
35
MediumFind First and Last Position of Element in Sorted Arrayβœ“ Our Solution
52
ArrayBinary Search
36
MediumSubsetsβœ“ Our Solution
52
ArrayBacktrackingBit Manipulation
37
48
MathBinary Search
38
MediumSet Matrix Zeroesβœ“ Our Solution
48
ArrayHash TableMatrix
39
MediumLetter Combinations of a Phone Numberβœ“ Our Solution
48
Hash TableStringBacktracking
40
MediumDivide Two Integersβœ“ Our Solution
48
MathBit Manipulation
41
EasyPascal's Triangleβœ“ Our Solution
48
ArrayDynamic Programming
42
MediumMaximum Subarrayβœ“ Our Solution
48
ArrayDivide and ConquerDynamic Programming
43
MediumBinary Tree Level Order Traversalβœ“ Our Solution
45
TreeBreadth-First SearchBinary Tree
44
MediumZigzag Conversionβœ“ Our Solution
45
String
45
MediumNext Permutationβœ“ Our Solution
45
ArrayTwo Pointers
46
HardRegular Expression Matchingβœ“ Our Solution
45
StringDynamic ProgrammingRecursion
47
MediumPow(x, n)βœ“ Our Solution
45
MathRecursion
48
EasyValid Palindromeβœ“ Our Solution
45
Two PointersString
49
HardLargest Rectangle in Histogramβœ“ Our Solution
45
ArrayStackMonotonic Stack
50
MediumGas Stationβœ“ Our Solution
40
ArrayGreedy
51
MediumSort Colorsβœ“ Our Solution
40
ArrayTwo PointersSorting
52
EasyLength of Last Wordβœ“ Our Solution
40
String
53
MediumSearch in Rotated Sorted Arrayβœ“ Our Solution
40
ArrayBinary Search
54
Medium3Sum Closestβœ“ Our Solution
40
ArrayTwo PointersSorting
55
MediumPermutationsβœ“ Our Solution
40
ArrayBacktracking
56
MediumLongest Consecutive Sequenceβœ“ Our Solution
40
ArrayHash TableUnion Find
57
EasySingle Numberβœ“ Our Solution
40
ArrayBit Manipulation
58
MediumValidate Binary Search Treeβœ“ Our Solution
40
TreeDepth-First SearchBinary Search TreeBinary Tree
59
MediumRecover Binary Search Treeβœ“ Our Solution
40
TreeDepth-First SearchBinary Search TreeBinary Tree
60
MediumSearch a 2D Matrixβœ“ Our Solution
40
ArrayBinary SearchMatrix
61
MediumMaximum Product Subarrayβœ“ Our Solution
34
ArrayDynamic Programming
62
EasySymmetric Treeβœ“ Our Solution
34
TreeDepth-First SearchBreadth-First SearchBinary Tree
63
MediumBest Time to Buy and Sell Stock IIβœ“ Our Solution
34
ArrayDynamic ProgrammingGreedy
64
EasyBinary Tree Preorder Traversalβœ“ Our Solution
34
StackTreeDepth-First SearchBinary Tree
65
MediumUnique Pathsβœ“ Our Solution
34
MathDynamic ProgrammingCombinatorics
66
MediumRemove Duplicates from Sorted Array IIβœ“ Our Solution
34
ArrayTwo Pointers
67
MediumString to Integer (atoi)βœ“ Our Solution
34
String
68
MediumValid Sudokuβœ“ Our Solution
34
ArrayHash TableMatrix
69
MediumInteger to Romanβœ“ Our Solution
34
Hash TableMathString
70
34
ArrayTwo PointersSorting
71
MediumRemove Nth Node From End of Listβœ“ Our Solution
34
Linked ListTwo Pointers
72
HardSudoku Solverβœ“ Our Solution
34
ArrayHash TableBacktrackingMatrix
73
MediumSearch in Rotated Sorted Array IIβœ“ Our Solution
26
ArrayBinary Search
74
HardReverse Nodes in k-Groupβœ“ Our Solution
26
Linked ListRecursion
75
MediumPalindrome Partitioningβœ“ Our Solution
26
StringDynamic ProgrammingBacktracking
76
MediumClone Graphβœ“ Our Solution
26
Hash TableDepth-First SearchBreadth-First SearchGraph
77
HardLongest Valid Parenthesesβœ“ Our Solution
26
StringDynamic ProgrammingStack
78
HardMerge k Sorted Listsβœ“ Our Solution
26
Linked ListDivide and ConquerHeap (Priority Queue)Merge Sort
79
MediumSingle Number IIβœ“ Our Solution
26
ArrayBit Manipulation
80
MediumCopy List with Random Pointerβœ“ Our Solution
26
Hash TableLinked List
81
MediumReorder Listβœ“ Our Solution
26
Linked ListTwo PointersStackRecursion
82
MediumSort Listβœ“ Our Solution
26
Linked ListTwo PointersDivide and ConquerSorting+1
83
HardWord Ladderβœ“ Our Solution
26
Hash TableStringBreadth-First Search
84
26
ArrayBacktracking
85
HardMaximal Rectangleβœ“ Our Solution
26
ArrayDynamic ProgrammingStackMatrix+1
86
MediumInsert Intervalβœ“ Our Solution
26
Array
87
EasyPascal's Triangle IIβœ“ Our Solution
26
ArrayDynamic Programming
88
MediumRotate Listβœ“ Our Solution
26
Linked ListTwo Pointers
89
MediumFlatten Binary Tree to Linked Listβœ“ Our Solution
26
Linked ListStackTreeDepth-First Search+1
90
MediumConstruct Binary Tree from Preorder and Inorder Traversalβœ“ Our Solution
26
ArrayHash TableDivide and ConquerTree+1
91
MediumUnique Paths IIβœ“ Our Solution
26
ArrayDynamic ProgrammingMatrix
92
MediumMinimum Path Sumβœ“ Our Solution
26
ArrayDynamic ProgrammingMatrix
93
MediumSimplify Pathβœ“ Our Solution
26
StringStack
94
EasySame Treeβœ“ Our Solution
26
TreeDepth-First SearchBreadth-First SearchBinary Tree
95
MediumEdit Distanceβœ“ Our Solution
26
StringDynamic Programming
96
HardMinimum Window Substringβœ“ Our Solution
26
Hash TableStringSliding Window
97
MediumInterleaving Stringβœ“ Our Solution
26
StringDynamic Programming
98
MediumUnique Binary Search Treesβœ“ Our Solution
26
MathDynamic ProgrammingTreeBinary Search Tree+1
99
MediumReverse Linked List IIβœ“ Our Solution
26
Linked List
100
MediumFind Minimum in Rotated Sorted Arrayβœ“ Our Solution
26
ArrayBinary Search