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Hash Table

239 questions

1Isomorphic StringsEasy
Hash TableString
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2Permutation in StringMedium
Hash TableTwo PointersString
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3Design Underground SystemMedium
Hash TableStringDesign
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4Sort Characters By FrequencyMedium
Hash TableStringSorting
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5Ransom NoteEasy
Hash TableStringCounting
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6Longest Substring Without Repeating CharactersMedium
Hash TableStringSliding Window
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7Maximum Number of BalloonsEasy
Hash TableStringCounting
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8Longest Substring Without Repeating CharactersMedium
Hash TableStringSliding Window
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9Longest Repeating Character ReplacementMedium
Hash TableStringSliding Window
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10Design Underground SystemMedium
Hash TableStringDesign
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11First Unique Character in a StringEasy
Hash TableStringQueue
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12Valid AnagramEasy
Hash TableStringSorting
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13LRU CacheMedium
Hash TableLinked ListDesign
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14Roman to IntegerEasy
Hash TableMathString
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15Word LadderHard
Hash TableStringBreadth-First Search
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16Letter Combinations of a Phone NumberMedium
Hash TableStringBacktracking
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17Substring with Concatenation of All WordsHard
Hash TableStringSliding Window
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18Sort Characters By FrequencyMedium
Hash TableStringSorting
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19Isomorphic StringsEasy
Hash TableString
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20Bulls and CowsMedium
Hash TableStringCounting
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21Reorganize StringMedium
Hash TableStringGreedy
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22Permutation in StringMedium
Hash TableTwo PointersString
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23Design A LeaderboardMedium
Hash TableDesignSorting
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24Time Based Key-Value StoreMedium
Hash TableStringBinary Search
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25Longest PalindromeEasy
Hash TableStringGreedy
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26Ransom NoteEasy
Hash TableStringCounting
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27Maximum Number of BalloonsEasy
Hash TableStringCounting
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28Longest Substring Without Repeating CharactersMedium
Hash TableStringSliding Window
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29Design Underground SystemMedium
Hash TableStringDesign
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30Longest Repeating Character ReplacementMedium
Hash TableStringSliding Window
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31Roman to IntegerEasy
Hash TableMathString
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32Valid AnagramEasy
Hash TableStringSorting
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33LRU CacheMedium
Hash TableLinked ListDesign
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34First Unique Character in a StringEasy
Hash TableStringQueue
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35Word LadderHard
Hash TableStringBreadth-First Search
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36Design A LeaderboardMedium
Hash TableDesignSorting
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37Remove Letter To Equalize FrequencyEasy
Hash TableStringCounting
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38Copy List with Random PointerMedium
Hash TableLinked List
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39Letter Combinations of a Phone NumberMedium
Hash TableStringBacktracking
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40Isomorphic StringsEasy
Hash TableString
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41Vertical Order Traversal of a Binary TreeHard
Hash TableTreeDepth-First Search
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42Time Based Key-Value StoreMedium
Hash TableStringBinary Search
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43Binary Tree Vertical Order TraversalMedium
Hash TableTreeDepth-First Search
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44Happy NumberEasy
Hash TableMathTwo Pointers
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45Integer to RomanMedium
Hash TableMathString
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46Linked List Cycle IIMedium
Hash TableLinked ListTwo Pointers
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47Permutation in StringMedium
Hash TableTwo PointersString
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48Sort Characters By FrequencyMedium
Hash TableStringSorting
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49Implement Magic DictionaryMedium
Hash TableStringDepth-First Search
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50Find the DifferenceEasy
Hash TableStringBit Manipulation
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51Implement Trie (Prefix Tree)Medium
Hash TableStringDesign
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52Repeated DNA SequencesMedium
Hash TableStringBit Manipulation
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53Ugly Number IIMedium
Hash TableMathDynamic Programming
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54Longest Balanced Substring IIMedium
Hash TableStringPrefix Sum
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55Linked List CycleEasy
Hash TableLinked ListTwo Pointers
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56Find All Anagrams in a StringMedium
Hash TableStringSliding Window
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57Substring with Concatenation of All WordsHard
Hash TableStringSliding Window
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58Bulls and CowsMedium
Hash TableStringCounting
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59Jewels and StonesEasy
Hash TableString
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60Reorganize StringMedium
Hash TableStringGreedy
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61Longest PalindromeEasy
Hash TableStringGreedy
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62Ransom NoteEasy
Hash TableStringCounting
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63Maximum Number of BalloonsEasy
Hash TableStringCounting
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64Longest Substring Without Repeating CharactersMedium
Hash TableStringSliding Window
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65Valid AnagramEasy
Hash TableStringSorting
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66LRU CacheMedium
Hash TableLinked ListDesign
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67Roman to IntegerEasy
Hash TableMathString
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68Design Underground SystemMedium
Hash TableStringDesign
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69First Unique Character in a StringEasy
Hash TableStringQueue
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70Binary Tree Vertical Order TraversalMedium
Hash TableTreeDepth-First Search
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71Longest Repeating Character ReplacementMedium
Hash TableStringSliding Window
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72Remove Letter To Equalize FrequencyEasy
Hash TableStringCounting
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73Isomorphic StringsEasy
Hash TableString
Solve →
74Vertical Order Traversal of a Binary TreeHard
Hash TableTreeDepth-First Search
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75Letter Combinations of a Phone NumberMedium
Hash TableStringBacktracking
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76Integer to RomanMedium
Hash TableMathString
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77Linked List CycleEasy
Hash TableLinked ListTwo Pointers
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78Design A LeaderboardMedium
Hash TableDesignSorting
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79Happy NumberEasy
Hash TableMathTwo Pointers
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80Copy List with Random PointerMedium
Hash TableLinked List
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81Minimum Number of Steps to Make Two Strings AnagramMedium
Hash TableStringCounting
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82Word LadderHard
Hash TableStringBreadth-First Search
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83Minimum Window SubstringHard
Hash TableStringSliding Window
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84Implement Magic DictionaryMedium
Hash TableStringDepth-First Search
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85Sort Characters By FrequencyMedium
Hash TableStringSorting
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86Reordered Power of 2Medium
Hash TableMathSorting
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87Implement Trie (Prefix Tree)Medium
Hash TableStringDesign
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88Permutation in StringMedium
Hash TableTwo PointersString
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89Ransom NoteEasy
Hash TableStringCounting
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90Linked List Cycle IIMedium
Hash TableLinked ListTwo Pointers
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91Intersection of Two Linked ListsEasy
Hash TableLinked ListTwo Pointers
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92Find All Anagrams in a StringMedium
Hash TableStringSliding Window
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93Repeated DNA SequencesMedium
Hash TableStringBit Manipulation
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94Find the DifferenceEasy
Hash TableStringBit Manipulation
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95Number of Substrings Containing All Three CharactersMedium
Hash TableStringSliding Window
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96Word PatternEasy
Hash TableString
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97Letter Tile PossibilitiesMedium
Hash TableStringBacktracking
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98Substring with Concatenation of All WordsHard
Hash TableStringSliding Window
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99Jewels and StonesEasy
Hash TableString
Solve →
100Word Ladder IIHard
Hash TableStringBacktracking
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101Clone GraphMedium
Hash TableDepth-First SearchBreadth-First Search
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102Reorganize StringMedium
Hash TableStringGreedy
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103Check if the Sentence Is PangramEasy
Hash TableString
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104Unique Length-3 Palindromic SubsequencesMedium
Hash TableStringBit Manipulation
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105Check if All Characters Have Equal Number of OccurrencesEasy
Hash TableStringCounting
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106Most Stones Removed with Same Row or ColumnMedium
Hash TableDepth-First SearchUnion-Find
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107Sum of Beauty of All SubstringsMedium
Hash TableStringCounting
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108Two Sum IV - Input is a BSTEasy
Hash TableTwo PointersTree
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109Next Greater Numerically Balanced NumberMedium
Hash TableMathBacktracking
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110Ugly Number IIMedium
Hash TableMathDynamic Programming
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111Longest PalindromeEasy
Hash TableStringGreedy
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112All O`one Data StructureHard
Hash TableLinked ListDesign
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113Minimum Genetic MutationMedium
Hash TableStringBreadth-First Search
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114Partition LabelsMedium
Hash TableTwo PointersString
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115Find the Longest Substring Containing Vowels in Even CountsMedium
Hash TableStringBit Manipulation
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116Remove Zero Sum Consecutive Nodes from Linked ListMedium
Hash TableLinked List
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117All Nodes Distance K in Binary TreeMedium
Hash TableTreeDepth-First Search
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118Find Root of N-Ary TreeMedium
Hash TableBit ManipulationTree
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119Design Task ManagerMedium
Hash TableDesignHeap (Priority Queue)
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120Design TwitterMedium
Hash TableLinked ListDesign
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121Find Duplicate SubtreesMedium
Hash TableTreeDepth-First Search
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122Amount of Time for Binary Tree to Be InfectedMedium
Hash TableTreeDepth-First Search
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123Custom Sort StringMedium
Hash TableStringSorting
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124Minimum Length of String After OperationsMedium
Hash TableStringCounting
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125Count Vowel Substrings of a StringEasy
Hash TableString
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126Longest Nice SubstringEasy
Hash TableStringDivide and Conquer
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127Construct K Palindrome StringsMedium
Hash TableStringGreedy
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128Minimum Deletions to Make String K-SpecialMedium
Hash TableStringGreedy
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129Maximum Manhattan Distance After K ChangesMedium
Hash TableMathString
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130Count of Substrings Containing Every Vowel and K Consonants IIMedium
Hash TableStringSliding Window
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131LFU CacheHard
Hash TableLinked ListDesign
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132Maximum Frequency StackHard
Hash TableStackDesign
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133Most Frequent Subtree SumMedium
Hash TableTreeDepth-First Search
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134Split a String Into the Max Number of Unique SubstringsMedium
Hash TableStringBacktracking
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135Palindrome PermutationEasy
Hash TableStringBit Manipulation
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136Lowest Common Ancestor of Deepest LeavesMedium
Hash TableTreeDepth-First Search
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137Count Largest GroupEasy
Hash TableMathCounting
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138Find Maximum Number of Non Intersecting SubstringsMedium
Hash TableStringDynamic Programming
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139Lexicographically Minimum String After Removing StarsMedium
Hash TableStringStack
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140Smallest Integer Divisible by KMedium
Hash TableMath
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141Fraction to Recurring DecimalMedium
Hash TableMathString
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142Smallest Subtree with all the Deepest NodesMedium
Hash TableTreeDepth-First Search
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143Smallest Number in Infinite SetMedium
Hash TableDesignHeap (Priority Queue)
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144Determine if Two Strings Are CloseMedium
Hash TableStringSorting
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145Longest Balanced Substring IMedium
Hash TableStringCounting
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146Take K of Each Character From Left and RightMedium
Hash TableStringSliding Window
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147Time Based Key-Value StoreMedium
Hash TableStringBinary Search
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148Longest Substring with At Least K Repeating CharactersMedium
Hash TableStringDivide and Conquer
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149Longest Substring Without Repeating CharactersMedium
Hash TableStringSliding Window
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150Valid AnagramEasy
Hash TableStringSorting
Solve →
151Roman to IntegerEasy
Hash TableMathString
Solve →
152LRU CacheMedium
Hash TableLinked ListDesign
Solve →
153Design Underground SystemMedium
Hash TableStringDesign
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154First Unique Character in a StringEasy
Hash TableStringQueue
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155Longest Repeating Character ReplacementMedium
Hash TableStringSliding Window
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156Remove Letter To Equalize FrequencyEasy
Hash TableStringCounting
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157Binary Tree Vertical Order TraversalMedium
Hash TableTreeDepth-First Search
Solve →
158Copy List with Random PointerMedium
Hash TableLinked List
Solve →
159Linked List CycleEasy
Hash TableLinked ListTwo Pointers
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160Isomorphic StringsEasy
Hash TableString
Solve →
161Vertical Order Traversal of a Binary TreeHard
Hash TableTreeDepth-First Search
Solve →
162Letter Combinations of a Phone NumberMedium
Hash TableStringBacktracking
Solve →
163Design A LeaderboardMedium
Hash TableDesignSorting
Solve →
164Word LadderHard
Hash TableStringBreadth-First Search
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165Integer to RomanMedium
Hash TableMathString
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166Happy NumberEasy
Hash TableMathTwo Pointers
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167Implement Trie (Prefix Tree)Medium
Hash TableStringDesign
Solve →
168Intersection of Two Linked ListsEasy
Hash TableLinked ListTwo Pointers
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169Minimum Number of Steps to Make Two Strings AnagramMedium
Hash TableStringCounting
Solve →
170Implement Magic DictionaryMedium
Hash TableStringDepth-First Search
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171Minimum Window SubstringHard
Hash TableStringSliding Window
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172Sort Characters By FrequencyMedium
Hash TableStringSorting
Solve →
173Permutation in StringMedium
Hash TableTwo PointersString
Solve →
174Linked List Cycle IIMedium
Hash TableLinked ListTwo Pointers
Solve →
175Ransom NoteEasy
Hash TableStringCounting
Solve →
176Find All Anagrams in a StringMedium
Hash TableStringSliding Window
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177Reordered Power of 2Medium
Hash TableMathSorting
Solve →
178Substring with Concatenation of All WordsHard
Hash TableStringSliding Window
Solve →
179Repeated DNA SequencesMedium
Hash TableStringBit Manipulation
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180Palindrome PermutationEasy
Hash TableStringBit Manipulation
Solve →
181Find the DifferenceEasy
Hash TableStringBit Manipulation
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182Number of Substrings Containing All Three CharactersMedium
Hash TableStringSliding Window
Solve →
183Letter Tile PossibilitiesMedium
Hash TableStringBacktracking
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184Jewels and StonesEasy
Hash TableString
Solve →
185Word PatternEasy
Hash TableString
Solve →
186Reorganize StringMedium
Hash TableStringGreedy
Solve →
187Word Ladder IIHard
Hash TableStringBacktracking
Solve →
188Clone GraphMedium
Hash TableDepth-First SearchBreadth-First Search
Solve →
189Check if the Sentence Is PangramEasy
Hash TableString
Solve →
190Ugly Number IIMedium
Hash TableMathDynamic Programming
Solve →
191Longest PalindromeEasy
Hash TableStringGreedy
Solve →
192Time Based Key-Value StoreMedium
Hash TableStringBinary Search
Solve →
193Most Stones Removed with Same Row or ColumnMedium
Hash TableDepth-First SearchUnion-Find
Solve →
194Two Sum IV - Input is a BSTEasy
Hash TableTwo PointersTree
Solve →
195Check if All Characters Have Equal Number of OccurrencesEasy
Hash TableStringCounting
Solve →
196Unique Length-3 Palindromic SubsequencesMedium
Hash TableStringBit Manipulation
Solve →
197Next Greater Numerically Balanced NumberMedium
Hash TableMathBacktracking
Solve →
198Sum of Beauty of All SubstringsMedium
Hash TableStringCounting
Solve →
199Find Root of N-Ary TreeMedium
Hash TableBit ManipulationTree
Solve →
200All Nodes Distance K in Binary TreeMedium
Hash TableTreeDepth-First Search
Solve →
201All O`one Data StructureHard
Hash TableLinked ListDesign
Solve →
202Minimum Genetic MutationMedium
Hash TableStringBreadth-First Search
Solve →
203Partition LabelsMedium
Hash TableTwo PointersString
Solve →
204Find the Longest Substring Containing Vowels in Even CountsMedium
Hash TableStringBit Manipulation
Solve →
205Remove Zero Sum Consecutive Nodes from Linked ListMedium
Hash TableLinked List
Solve →
206Maximum Manhattan Distance After K ChangesMedium
Hash TableMathString
Solve →
207Design Task ManagerMedium
Hash TableDesignHeap (Priority Queue)
Solve →
208Design TwitterMedium
Hash TableLinked ListDesign
Solve →
209LFU CacheHard
Hash TableLinked ListDesign
Solve →
210Find Duplicate SubtreesMedium
Hash TableTreeDepth-First Search
Solve →
211Custom Sort StringMedium
Hash TableStringSorting
Solve →
212Amount of Time for Binary Tree to Be InfectedMedium
Hash TableTreeDepth-First Search
Solve →
213Count Vowel Substrings of a StringEasy
Hash TableString
Solve →
214Construct K Palindrome StringsMedium
Hash TableStringGreedy
Solve →
215Minimum Length of String After OperationsMedium
Hash TableStringCounting
Solve →
216Longest Nice SubstringEasy
Hash TableStringDivide and Conquer
Solve →
217Count of Substrings Containing Every Vowel and K Consonants IIMedium
Hash TableStringSliding Window
Solve →
218Lowest Common Ancestor of Deepest LeavesMedium
Hash TableTreeDepth-First Search
Solve →
219Count Largest GroupEasy
Hash TableMathCounting
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220Minimum Deletions to Make String K-SpecialMedium
Hash TableStringGreedy
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221Longest Balanced Substring IMedium
Hash TableStringCounting
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222Maximum Frequency StackHard
Hash TableStackDesign
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223Longest Substring with At Least K Repeating CharactersMedium
Hash TableStringDivide and Conquer
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224Determine if Two Strings Are CloseMedium
Hash TableStringSorting
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225Smallest Subtree with all the Deepest NodesMedium
Hash TableTreeDepth-First Search
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226Take K of Each Character From Left and RightMedium
Hash TableStringSliding Window
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227Longest Balanced Substring IIMedium
Hash TableStringPrefix Sum
Solve →
228Bulls and CowsMedium
Hash TableStringCounting
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229Most Frequent Subtree SumMedium
Hash TableTreeDepth-First Search
Solve →
230Split a String Into the Max Number of Unique SubstringsMedium
Hash TableStringBacktracking
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231Find Maximum Number of Non Intersecting SubstringsMedium
Hash TableStringDynamic Programming
Solve →
232Lexicographically Minimum String After Removing StarsMedium
Hash TableStringStack
Solve →
233Fraction to Recurring DecimalMedium
Hash TableMathString
Solve →
234Smallest Integer Divisible by KMedium
Hash TableMath
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235Minimize String LengthEasy
Hash TableString
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236Smallest Number in Infinite SetMedium
Hash TableDesignHeap (Priority Queue)
Solve →
237Substrings of Size Three with Distinct CharactersEasy
Hash TableStringSliding Window
Solve →
238Stock Price FluctuationMedium
Hash TableDesignHeap (Priority Queue)
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239Maximum Number of BalloonsEasy
Hash TableStringCounting
Solve →