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Title	Difficulty	Topics
1. Two Sum	Easy	ArrayHash Table
4. Median of Two Sorted Arrays	Hard	ArrayBinary SearchDivide and Conquer
11. Container With Most Water	Medium	ArrayTwo PointersGreedy
14. Longest Common Prefix	Easy	ArrayStringTrie
15. 3Sum	Medium	ArrayTwo PointersSorting
16. 3Sum Closest	Medium	ArrayTwo PointersSorting
18. 4Sum	Medium	ArrayTwo PointersSorting
26. Remove Duplicates from Sorted Array	Easy	ArrayTwo Pointers
27. Remove Element	Easy	ArrayTwo Pointers
31. Next Permutation	Medium	ArrayTwo Pointers
33. Search in Rotated Sorted Array	Medium	ArrayBinary Search
34. Find First and Last Position of Element in Sorted Array	Medium	ArrayBinary Search
35. Search Insert Position	Easy	ArrayBinary Search
36. Valid Sudoku	Medium	ArrayHash TableMatrix
37. Sudoku Solver	Hard	ArrayHash TableBacktracking+1 more
39. Combination Sum	Medium	ArrayBacktracking
40. Combination Sum II	Medium	ArrayBacktracking
41. First Missing Positive	Hard	ArrayHash Table
42. Trapping Rain Water	Hard	ArrayTwo PointersDynamic Programming+2 more
45. Jump Game II	Medium	ArrayDynamic ProgrammingGreedy
46. Permutations	Medium	ArrayBacktracking
47. Permutations II	Medium	ArrayBacktrackingSorting
48. Rotate Image	Medium	ArrayMathMatrix
49. Group Anagrams	Medium	ArrayHash TableString+1 more
51. N-Queens	Hard	ArrayBacktracking
53. Maximum Subarray	Medium	ArrayDivide and ConquerDynamic Programming
54. Spiral Matrix	Medium	ArrayMatrixSimulation
55. Jump Game	Medium	ArrayDynamic ProgrammingGreedy
56. Merge Intervals	Medium	ArraySorting
57. Insert Interval	Medium	Array
59. Spiral Matrix II	Medium	ArrayMatrixSimulation
63. Unique Paths II	Medium	ArrayDynamic ProgrammingMatrix
64. Minimum Path Sum	Medium	ArrayDynamic ProgrammingMatrix
66. Plus One	Easy	ArrayMath
68. Text Justification	Hard	ArrayStringSimulation
73. Set Matrix Zeroes	Medium	ArrayHash TableMatrix
74. Search a 2D Matrix	Medium	ArrayBinary SearchMatrix
75. Sort Colors	Medium	ArrayTwo PointersSorting
78. Subsets	Medium	ArrayBacktrackingBit Manipulation
79. Word Search	Medium	ArrayStringBacktracking+2 more
80. Remove Duplicates from Sorted Array II	Medium	ArrayTwo Pointers
81. Search in Rotated Sorted Array II	Medium	ArrayBinary Search
84. Largest Rectangle in Histogram	Hard	ArrayStackMonotonic Stack
85. Maximal Rectangle	Hard	ArrayDynamic ProgrammingStack+2 more
88. Merge Sorted Array	Easy	ArrayTwo PointersSorting
90. Subsets II	Medium	ArrayBacktrackingBit Manipulation
105. Construct Binary Tree from Preorder and Inorder Traversal	Medium	ArrayHash TableDivide and Conquer+2 more
106. Construct Binary Tree from Inorder and Postorder Traversal	Medium	ArrayHash TableDivide and Conquer+2 more
108. Convert Sorted Array to Binary Search Tree	Easy	ArrayDivide and ConquerTree+2 more
118. Pascal's Triangle	Easy	ArrayDynamic Programming
119. Pascal's Triangle II	Easy	ArrayDynamic Programming
120. Triangle	Medium	ArrayDynamic Programming
121. Best Time to Buy and Sell Stock	Easy	ArrayDynamic Programming
122. Best Time to Buy and Sell Stock II	Medium	ArrayDynamic ProgrammingGreedy
123. Best Time to Buy and Sell Stock III	Hard	ArrayDynamic Programming
128. Longest Consecutive Sequence	Medium	ArrayHash TableUnion-Find
130. Surrounded Regions	Medium	ArrayDepth-First SearchBreadth-First Search+2 more
134. Gas Station	Medium	ArrayGreedy
135. Candy	Hard	ArrayGreedy
136. Single Number	Easy	ArrayBit Manipulation
137. Single Number II	Medium	ArrayBit Manipulation
139. Word Break	Medium	ArrayHash TableString+3 more
140. Word Break II	Hard	ArrayHash TableString+4 more
149. Max Points on a Line	Hard	ArrayHash TableMath+1 more
150. Evaluate Reverse Polish Notation	Medium	ArrayMathStack
152. Maximum Product Subarray	Medium	ArrayDynamic Programming
153. Find Minimum in Rotated Sorted Array	Medium	ArrayBinary Search
154. Find Minimum in Rotated Sorted Array II	Hard	ArrayBinary Search
157. Read N Characters Given Read4Premium	Easy	ArraySimulationInteractive
158. Read N Characters Given read4 II - Call Multiple TimesPremium	Hard	ArraySimulationInteractive
162. Find Peak Element	Medium	ArrayBinary Search
163. Missing RangesPremium	Easy	Array
164. Maximum Gap	Medium	ArraySortingBucket Sort+1 more
167. Two Sum II - Input Array Is Sorted	Medium	ArrayTwo PointersBinary Search
169. Majority Element	Easy	ArrayHash TableDivide and Conquer+2 more
170. Two Sum III - Data structure designPremium	Easy	ArrayHash TableTwo Pointers+2 more
174. Dungeon Game	Hard	ArrayDynamic ProgrammingMatrix
179. Largest Number	Medium	ArrayStringGreedy+1 more
188. Best Time to Buy and Sell Stock IV	Hard	ArrayDynamic Programming
189. Rotate Array	Medium	ArrayMathTwo Pointers
198. House Robber	Medium	ArrayDynamic Programming
200. Number of Islands	Medium	ArrayDepth-First SearchBreadth-First Search+2 more
204. Count Primes	Medium	ArrayMathEnumeration+1 more
209. Minimum Size Subarray Sum	Medium	ArrayBinary SearchSliding Window+1 more
212. Word Search II	Hard	ArrayStringBacktracking+2 more
213. House Robber II	Medium	ArrayDynamic Programming
215. Kth Largest Element in an Array	Medium	ArrayDivide and ConquerSorting+2 more
216. Combination Sum III	Medium	ArrayBacktracking
217. Contains Duplicate	Easy	ArrayHash TableSorting
218. The Skyline Problem	Hard	ArrayDivide and ConquerBinary Indexed Tree+5 more
219. Contains Duplicate II	Easy	ArrayHash TableSliding Window
220. Contains Duplicate III	Hard	ArraySliding WindowSorting+2 more
221. Maximal Square	Medium	ArrayDynamic ProgrammingMatrix
228. Summary Ranges	Easy	Array
229. Majority Element II	Medium	ArrayHash TableSorting+1 more
238. Product of Array Except Self	Medium	ArrayPrefix Sum
239. Sliding Window Maximum	Hard	ArrayQueueSliding Window+2 more
240. Search a 2D Matrix II	Medium	ArrayBinary SearchDivide and Conquer+1 more
243. Shortest Word DistancePremium	Easy	ArrayString
244. Shortest Word Distance IIPremium	Medium	ArrayHash TableTwo Pointers+2 more
245. Shortest Word Distance IIIPremium	Medium	ArrayString
247. Strobogrammatic Number IIPremium	Medium	ArrayStringRecursion
248. Strobogrammatic Number IIIPremium	Hard	ArrayStringRecursion
249. Group Shifted StringsPremium	Medium	ArrayHash TableString