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