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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
HardTrapping Rain Waterβœ“ Our Solution
86
ArrayTwo PointersDynamic ProgrammingStack+1
3
MediumLongest Substring Without Repeating Charactersβœ“ Our Solution
83
Hash TableStringSliding Window
4
EasyMerge Sorted Arrayβœ“ Our Solution
81
ArrayTwo PointersSorting
5
MediumGroup Anagramsβœ“ Our Solution
79
ArrayHash TableStringSorting
6
MediumAdd Two Numbersβœ“ Our Solution
78
Linked ListMathRecursion
7
EasyValid Parenthesesβœ“ Our Solution
78
StringStack
8
MediumLongest Palindromic Substringβœ“ Our Solution
77
Two PointersStringDynamic Programming
9
77
ArrayTwo PointersSorting
10
MediumMerge Intervalsβœ“ Our Solution
76
ArraySorting
11
HardMedian of Two Sorted Arraysβœ“ Our Solution
75
ArrayBinary SearchDivide and Conquer
12
MediumContainer With Most Waterβœ“ Our Solution
75
ArrayTwo PointersGreedy
13
HardMerge k Sorted Listsβœ“ Our Solution
71
Linked ListDivide and ConquerHeap (Priority Queue)Merge Sort
14
MediumMaximum Subarrayβœ“ Our Solution
71
ArrayDivide and ConquerDynamic Programming
15
EasyLongest Common Prefixβœ“ Our Solution
71
StringTrie
16
EasyClimbing Stairsβœ“ Our Solution
70
MathDynamic ProgrammingMemoization
17
MediumJump Gameβœ“ Our Solution
70
ArrayDynamic ProgrammingGreedy
18
MediumGenerate Parenthesesβœ“ Our Solution
69
StringDynamic ProgrammingBacktracking
19
MediumLetter Combinations of a Phone Numberβœ“ Our Solution
68
Hash TableStringBacktracking
20
MediumSpiral Matrixβœ“ Our Solution
67
ArrayMatrixSimulation
21
MediumSearch in Rotated Sorted Arrayβœ“ Our Solution
67
ArrayBinary Search
22
EasyPalindrome Numberβœ“ Our Solution
67
Math
23
EasyRoman to Integerβœ“ Our Solution
66
Hash TableMathString
24
EasyMerge Two Sorted Listsβœ“ Our Solution
66
Linked ListRecursion
25
MediumReverse Integerβœ“ Our Solution
65
Math
26
MediumRotate Imageβœ“ Our Solution
64
ArrayMathMatrix
27
MediumWord Searchβœ“ Our Solution
64
ArrayStringBacktrackingDepth-First Search+1
28
MediumNext Permutationβœ“ Our Solution
63
ArrayTwo Pointers
29
EasyRemove Duplicates from Sorted Arrayβœ“ Our Solution
63
ArrayTwo Pointers
30
HardLargest Rectangle in Histogramβœ“ Our Solution
62
ArrayStackMonotonic Stack
31
MediumValid Sudokuβœ“ Our Solution
61
ArrayHash TableMatrix
32
MediumFind First and Last Position of Element in Sorted Arrayβœ“ Our Solution
61
ArrayBinary Search
33
HardFirst Missing Positiveβœ“ Our Solution
59
ArrayHash Table
34
MediumJump Game IIβœ“ Our Solution
59
ArrayDynamic ProgrammingGreedy
35
MediumSubsetsβœ“ Our Solution
59
ArrayBacktrackingBit Manipulation
36
MediumSet Matrix Zeroesβœ“ Our Solution
59
ArrayHash TableMatrix
37
58
ArrayTwo PointersSorting
38
HardReverse Nodes in k-Groupβœ“ Our Solution
57
Linked ListRecursion
39
MediumPow(x, n)βœ“ Our Solution
57
MathRecursion
40
MediumUnique Pathsβœ“ Our Solution
57
MathDynamic ProgrammingCombinatorics
41
MediumSort Colorsβœ“ Our Solution
56
ArrayTwo PointersSorting
42
MediumSearch a 2D Matrixβœ“ Our Solution
56
ArrayBinary SearchMatrix
43
HardRegular Expression Matchingβœ“ Our Solution
56
StringDynamic ProgrammingRecursion
44
HardMinimum Window Substringβœ“ Our Solution
55
Hash TableStringSliding Window
45
MediumRemove Nth Node From End of Listβœ“ Our Solution
55
Linked ListTwo Pointers
46
MediumValidate Binary Search Treeβœ“ Our Solution
54
TreeDepth-First SearchBinary Search TreeBinary Tree
47
54
ArrayBacktracking
48
MediumZigzag Conversionβœ“ Our Solution
53
String
49
MediumCombination Sumβœ“ Our Solution
53
ArrayBacktracking
50
EasyRemove Elementβœ“ Our Solution
53
ArrayTwo Pointers
51
EasyFind the Index of the First Occurrence in a Stringβœ“ Our Solution
53
Two PointersStringString Matching
52
MediumInteger to Romanβœ“ Our Solution
52
Hash TableMathString
53
51
MathBinary Search
54
51
ArrayMath
55
MediumPermutationsβœ“ Our Solution
50
ArrayBacktracking
56
EasySearch Insert Positionβœ“ Our Solution
49
ArrayBinary Search
57
HardLongest Valid Parenthesesβœ“ Our Solution
49
StringDynamic ProgrammingStack
58
MediumReverse Linked List IIβœ“ Our Solution
47
Linked List
59
MediumString to Integer (atoi)βœ“ Our Solution
47
String
60
MediumEdit Distanceβœ“ Our Solution
46
StringDynamic Programming
61
EasyAdd Binaryβœ“ Our Solution
46
MathStringBit ManipulationSimulation
62
MediumDivide Two Integersβœ“ Our Solution
46
MathBit Manipulation
63
MediumSwap Nodes in Pairsβœ“ Our Solution
46
Linked ListRecursion
64
MediumSimplify Pathβœ“ Our Solution
45
StringStack
65
MediumDecode Waysβœ“ Our Solution
45
StringDynamic Programming
66
MediumMinimum Path Sumβœ“ Our Solution
44
ArrayDynamic ProgrammingMatrix
67
MediumRemove Duplicates from Sorted Array IIβœ“ Our Solution
44
ArrayTwo Pointers
68
MediumRotate Listβœ“ Our Solution
44
Linked ListTwo Pointers
69
MediumSubsets IIβœ“ Our Solution
44
ArrayBacktrackingBit Manipulation
70
MediumCombination Sum IIβœ“ Our Solution
44
ArrayBacktracking
71
EasySame Treeβœ“ Our Solution
43
TreeDepth-First SearchBreadth-First SearchBinary Tree
72
EasyLength of Last Wordβœ“ Our Solution
43
String
73
Medium3Sum Closestβœ“ Our Solution
43
ArrayTwo PointersSorting
74
HardSudoku Solverβœ“ Our Solution
43
ArrayHash TableBacktrackingMatrix
75
MediumInsert Intervalβœ“ Our Solution
43
Array
76
HardWildcard Matchingβœ“ Our Solution
42
StringDynamic ProgrammingGreedyRecursion
77
MediumCount and Sayβœ“ Our Solution
40
String
78
MediumSearch in Rotated Sorted Array IIβœ“ Our Solution
40
ArrayBinary Search
79
EasyRemove Duplicates from Sorted Listβœ“ Our Solution
39
Linked List
80
EasyBinary Tree Inorder Traversalβœ“ Our Solution
38
StackTreeDepth-First SearchBinary Tree
81
MediumMultiply Stringsβœ“ Our Solution
38
MathStringSimulation
82
HardText Justificationβœ“ Our Solution
37
ArrayStringSimulation
83
HardMaximal Rectangleβœ“ Our Solution
36
ArrayDynamic ProgrammingStackMatrix+1
84
MediumUnique Binary Search Trees IIβœ“ Our Solution
35
Dynamic ProgrammingBacktrackingTreeBinary Search Tree+1
85
MediumPartition Listβœ“ Our Solution
35
Linked ListTwo Pointers
86
MediumUnique Paths IIβœ“ Our Solution
35
ArrayDynamic ProgrammingMatrix
87
HardPermutation Sequenceβœ“ Our Solution
34
MathRecursion
88
HardSubstring with Concatenation of All Wordsβœ“ Our Solution
33
Hash TableStringSliding Window
89
MediumCombinationsβœ“ Our Solution
32
Backtracking
90
MediumRecover Binary Search Treeβœ“ Our Solution
31
TreeDepth-First SearchBinary Search TreeBinary Tree
91
MediumInterleaving Stringβœ“ Our Solution
28
StringDynamic Programming
92
MediumPermutations IIβœ“ Our Solution
28
ArrayBacktrackingSorting
93
MediumGray Codeβœ“ Our Solution
27
MathBacktrackingBit Manipulation
94
MediumUnique Binary Search Treesβœ“ Our Solution
27
MathDynamic ProgrammingTreeBinary Search Tree+1
95
MediumSpiral Matrix IIβœ“ Our Solution
24
ArrayMatrixSimulation
96
MediumRestore IP Addressesβœ“ Our Solution
24
StringBacktracking
97
MediumRemove Duplicates from Sorted List IIβœ“ Our Solution
22
Linked ListTwo Pointers
98
HardValid Numberβœ“ Our Solution
20
String
99
HardN-Queens IIβœ“ Our Solution
16
Backtracking
100
HardScramble Stringβœ“ Our Solution
13
StringDynamic Programming