README.md

Java Algorithm Problems

程序员的一天

从开始这个Github已经有将近两年时间, 很高兴这个repo可以帮到有需要的人. 我一直认为, 知识本身是无价的, 因此每逢闲暇, 我就会来维护这个repo, 给刷题的朋友们一些我的想法和见解. 下面来简单介绍一下这个repo:

README.md: 所有所做过的题目

ReviewPage.md: 所有题目的总结和归纳（不断完善中）

KnowledgeHash2.md: 对所做过的知识点的一些笔记

SystemDesign.md: 对系统设计的一些笔记

Future Milestone: 我准备将一些有意思的题目，做成视频的形式给大家参考

希望大家学习顺利, 对未来充满希望(程序员也是找到好老板的!) 有问题可以给我写邮件([email protected]), 或者在GitHub上发issue给我.

Squence Problem Level Language Tags Video Tutorial 0 Alien Dictionary.java Hard Java []

1 Anagrams.java Medium Java []

2 Binary Representation.java Hard Java []

3 Binary Tree Level Order Traversal II.java Medium Java []

4 Binary Tree Level Order Traversal.java Medium Java []

5 Binary Tree Longest Consecutive Sequence.java Medium Java []

6 Binary Tree Maximum Path Sum II.java Medium Java []

7 Binary Tree Preorder Traversal.java Easy Java []

8 Binary Tree Right Side View.java Medium Java []

9 Binary Tree Serialization.java Medium Java []

10 Binary Tree Zigzag Level Order Traversal.java Medium Java []

11 Closest Number in Sorted Array.java Easy Java []

12 ColorGrid.java Medium Java []

13 Combination Sum II.java Medium Java []

14 Combination Sum.java Medium Java []

15 Combinations.java Medium Java []

16 Compare Strings.java Easy Java []

17 Complete Binary Tree.java Easy Java []

18 Construct Binary Tree from Inorder and Postorder Traversal.java Medium Java []

19 Container With Most Water.java Medium Java []

20 Contains Duplicate II.java Easy Java []

21 Contains Duplicate III.java Medium Java []

22 Contains Duplicate.java Easy Java []

23 Convert Binary Search Tree to Doubly Linked List.java Medium Java []

24 Convert Expression to Polish Notation.java Hard Java []

25 Convert Expression to Reverse Polish Notation.java Hard Java []

26 Convert Integer A to Integer B.java Easy Java []

27 Copy List with Random Pointer.java Medium Java []

28 Cosine Similarity.java Easy Java []

29 Count 1 in Binary.java Easy Java []

30 Count and Say.java Easy Java []

31 Count of Smaller Number before itself.java Hard Java []

32 Count of Smaller Number.java Medium Java []

33 Count Primes.java Easy Java []

34 Delete Digits.java Medium Java []

35 Delete Node in the Middle of Singly Linked List.java Easy Java []

36 Encode and Decode Strings.java Medium Java []

37 ExcelSheetColumnNumber .java Easy Java []

38 Expression Evaluation.java Hard Java []

39 Expression Tree Build.java Hard Java []

40 Fast Power.java Medium Java []

41 Fibonacci.java Easy Java []

42 Find the Connected Component in the Undirected Graph.java Medium Java []

43 Find the Weak Connected Component in the Directed Graph.java Medium Java []

44 First Missing Positive.java N/A Java []

45 Flatten 2D Vector.java Medium Java []

46 Flip Game II.java Medium Java []

47 Flip Game.java Easy Java []

48 Fraction to Recurring Decimal.java Medium Java []

49 Gas Station.java N/A Java []

50 Generate Parentheses.java Medium Java []

51 Gray Code.java Medium Java []

52 Group Anagrams.java Medium Java []

53 Group Shifted Strings.java Easy Java []

54 H-Index II.java Medium Java []

55 H-Index.java Medium Java []

56 Hamming Distance.java Easy Java []

57 Happy Number.java Easy Java []

58 Hash Function.java Easy Java []

59 HashHeap.java Hard Java []

60 HashWithArray.java Easy Java []

61 HashWithCustomizedClass(LinkedList).java Medium Java []

62 Heapify.java Medium Java []

63 Heaters.java Easy Java []

64 Identical Binary Tree.java Easy Java []

65 Implement Queue by Two Stacks.java N/A Java []

66 Implement Stack by Two Queues.java Easy Java []

67 Implement Stack using Queues.java Easy Java []

68 Implement Stack.java Easy Java []

69 Implement strStr().java N/A Java []

70 Implement Trie (Prefix Tree).java Medium Java []

71 IndexMatch.java Easy Java []

72 Inorder Successor in Binary Search Tree.java Medium Java []

73 Insert Interval.java Easy Java []

74 Insert Node in a Binary Search Tree .java Easy Java []

75 Insertion Sort List.java N/A Java []

76 Integer to English Words.java N/A Java []

77 Interleaving Positive and Negative Numbers.java N/A Java []

78 Intersection of Two Arrays.java Easy Java []

79 Intersection of Two Linked Lists.java Easy Java []

80 Interval Minimum Number.java Medium Java []

81 Interval Sum II.java Hard Java []

82 Interval Sum.java Medium Java []

83 Invert Binary Tree.java Easy Java []

84 Isomorphic Strings.java Easy Java []

85 Jump Game II.java Hard Java []

86 Kth Largest Element.java Medium Java []

87 Kth Smallest Element in a BST.java N/A Java []

88 Kth Smallest Sum In Two Sorted Arrays.java Hard Java []

89 Largest Number.java N/A Java []

90 Last Position of Target.java N/A Java []

91 Length of Last Word.java N/A Java []

92 Longest Common Prefix.java Medium Java []

93 Longest Common Substring.java N/A Java []

94 Longest Consecutive Sequence.java N/A Java []

95 Longest Increasing Continuous subsequence II.java N/A Java []

96 Longest Increasing Continuous subsequence.java Easy Java []

97 Longest Palindromic Substring.java Medium Java []

98 Longest Univalue Path.java Easy Java []

99 Longest Word in Dictionary.java Easy Java []

100 Longest Words.java N/A Java []

101 Lowest Common Ancestor II.java Easy Java []

102 Lowest Common Ancestor of a Binary Search Tree.java Medium Java []

103 Lowest Common Ancestor.java Easy Java []

104 LRU Cache.java Hard Java []

105 Majority Number II.java Medium Java []

106 Majority Number III.java Medium Java []

107 Matrix Zigzag Traversal.java Easy Java []

108 Max Area of Island.java Easy Java []

109 Maximum Depth of Binary Tree.java Easy Java []

110 Maximum Subarray III.java N/A Java []

111 Maximum Subarray.java Easy Java []

112 Maximum SubarrayII.java N/A Java []

113 MaximumSubarrayII.java N/A Java []

114 Median of two Sorted Arrays.java Hard Java []

115 Median.java N/A Java []

116 Merge Intervals.java Easy Java []

117 Merge k Sorted Arrays.java Medium Java []

118 Merge k Sorted Lists.java Medium Java []

119 Merge Sorted Array II.java N/A Java []

120 Merge Sorted Array.java Easy Java []

121 Merge Two Binary Trees.java Easy Java []

122 Merge Two Sorted Lists.java Easy Java []

123 Middle of Linked List.java N/A Java []

124 Minimum Absolute Difference in BST.java Easy Java []

125 Minimum Height Trees.java N/A Java []

126 Minimum Subarray.java N/A Java []

127 MinimumDepthOfBinaryTree.java Easy Java []

128 Missing Ranges.java N/A Java []

129 Multiply Strings.java Medium Java []

130 Next Permutation.java Medium Java []

131 Nim Game.java Easy Java []

132 NQueens.java N/A Java []

133 NQueensII.java N/A Java []

134 Nth to Last Node in List.java N/A Java []

135 Number Triangles.java N/A Java []

136 O(1) Check Power of 2.java N/A Java []

137 One Edit Distance.java Medium Java []

138 Paint Fence.java N/A Java []

139 Palindrome Linked List.java N/A Java []

140 Palindrome Partitioning.java N/A Java []

141 Palindrome Permutation II.java Medium Java []

142 Palindrome Permutation.java Easy Java []

143 Partition Array by Odd and Even.java N/A Java []

144 Partition Array.java N/A Java []

145 Partition List.java N/A Java []

146 Pascal's Triangle II.java Easy Java []

147 Peeking Iterator.java N/A Java []

148 Permutation Index.java Easy Java []

149 Permutation Sequence.java Medium Java []

150 Permutations II.java Medium Java []

151 Permutations.java Medium Java []

152 Populating Next Right Pointers in Each Node II.java Hard Java []

153 Product of Array Exclude Itself.java N/A Java []

154 QuickSort.java Easy Java []

155 Recover Rotated Sorted Array.java N/A Java []

156 Rehashing.java Medium Java []

157 Remove Duplicates from Sorted Array.java Easy Java []

158 Remove Duplicates from Sorted List II.java N/A Java []

159 Remove Duplicates from Sorted List.java Easy Java []

160 Remove Duplicates from Unsorted List.java N/A Java []

161 Remove Invalid Parentheses.java Hard Java []

162 Remove Linked List Elements.java N/A Java []

163 Remove Node in Binary Search Tree.java Hard Java []

164 Reorder List.java N/A Java []

165 Reshape the Matrix.java Easy Java []

166 Restore IP Addresses.java N/A Java []

167 Reverse Linked List II .java N/A Java []

168 Reverse Linked List.java Easy Java []

169 Reverse String.java Easy Java []

170 Reverse Words in a String II.java Medium Java []

171 Reverse Words in a String.java Medium Java []

172 Roman to Integer.java Easy Java []

173 Rotate Image.java Medium Java []

174 Rotate List.java N/A Java []

175 Rotate String.java N/A Java []

176 Russian Doll Envelopes.java N/A Java []

177 Search a 2D Matrix II.java N/A Java []

178 Search a 2D Matrix.java N/A Java []

179 Search for a Range.java N/A Java []

180 Search Insert Position.java N/A Java []

181 Search Range in Binary Search Tree .java Medium Java []

182 Search Rotated in Sorted Array II.java N/A Java []

183 Search Rotated in Sorted Array.java Hard Java []

184 Segment Tree Build II.java Medium Java []

185 Segment Tree Build.java Medium Java []

186 Segment Tree Modify.java Medium Java []

187 Segment Tree Query II.java Medium Java []

188 Segment Tree Query.java Medium Java []

189 Serilization and Deserialization Of Binary Tree.java N/A Java []

190 Shortest Word Distance.java Easy Java []

191 Single Number II.java N/A Java []

192 Single Number III.java N/A Java []

193 Single Number.java Easy Java []

194 Singleton.java N/A Java []

195 Sliding Window Maximum.java N/A Java []

196 Sort Color.java N/A Java []

197 Sort Colors II.java N/A Java []

198 Sort Letters by Case.java N/A Java []

199 Sort List.java N/A Java []

200 Space Replacement.java N/A Java []

201 Stone Game.java N/A Java []

202 String Permutation.java Easy Java []

203 String to Integer(atoi).java Easy Java []

204 Strobogrammatic Number II.java Medium Java []

205 Strobogrammatic Number.java Easy Java []

206 StrStr.java N/A Java []

207 Subarray Sum Closest.java Medium Java []

208 Subarray Sum.java Easy Java []

209 Subset.java Medium Java []

210 Subsets II.java Medium Java []

211 Subtree.java Easy Java []

212 Summary Ranges.java N/A Java []

213 Symmetric Binary Tree.java Easy Java []

214 The Smallest Difference.java N/A Java []

215 Top K Frequent Elements.java Medium Java []

216 Top K Frequent Words.java Medium Java []

217 Topological Sorting.java Medium Java []

218 Total Occurrence of Target.java N/A Java []

219 Trailing Zeros.java N/A Java []

220 Tweaked Identical Binary Tree.java Easy Java []

221 Two Lists Sum.java N/A Java []

222 Two Strings Are Anagrams.java Easy Java []

223 Ugly Number II.java N/A Java []

224 Ugly Number.java Medium Java []

225 Unique Binary Search Tree II.java N/A Java []

226 Unique Characters.java N/A Java []

227 Unique Word Abbreviation.java N/A Java []

228 Valid Palindrome.java Easy Java []

229 Valid Parentheses.java Easy Java []

230 Valid Sudoku.java Easy Java []

231 Word Break.java Medium Java []

232 Word Ladder II.java Hard Java []

233 Word Ladder.java Medium Java []

234 Word Pattern.java Easy Java []

235 Zigzag Iterator.java N/A Java []

236 Find Anagram Mappings.java Easy Java [Hash Table]

237 Judge Route Circle.java Easy Java [String]

238 Island Perimeter.java Easy Java [Hash Table]

239 First Unique Character in a String.java Easy Java [Hash Table, String]

240 Power of Three.java Easy Java [Math]

241 Plus One.java Easy Java [Array, Math]

242 Power of Two.java Easy Java [Bit Manipulation, Math]

243 Reverse Vowels of a String.java Easy Java [String, Two Pointers]

244 Guess Number Higher or Lower.java Easy Java [Binary Search]

245 Encode and Decode TinyURL.java Medium Java [Hash Table, Math]

246 Wiggle Sort.java Medium Java [Array, Sort]

247 Queue Reconstruction by Height.java Medium Java [Greedy]

248 2 Sum.java Easy Java [Array, Hash Table]

249 2 Sum II - Input array is sorted.java Medium Java [Array, Binary Search, Two Pointers]

250 2 Sum II.java Medium Java [Array, Binary Search, Two Pointers]

251 Coin Change.java Medium Java [DP]

252 Jump Game.java Medium Java [Array, Greedy]

253 Maximum Product Subarray.java Medium Java [Array, DP]

254 3 Sum Closest.java Medium Java [Array, Two Pointers]

255 Triangle Count.java Medium Java [Array]

256 3 Sum.java Medium Java [Array, Two Pointers]

257 4 Sum.java Medium Java [Hash Table]

258 k Sum.java Hard Java [DP]

259 Longest Continuous Increasing Subsequence.java Easy Java [Array, DP]

260 Longest Increasing Subsequence.java Medium Java [Binary Search, DP, Memoization, Sequence DP]

261 Unique Binary Search Tree.java Medium Java [DP, Tree]

262 Trim a Binary Search Tree.java Easy Java [Tree]

263 Unique Paths II.java Medium Java [Array, DP]

264 Counting Bits.java Medium Java [Bit Manipulation, DP]

265 Bomb Enemy.java Medium Java [DP]

266 Paint House.java Easy Java [DP]

267 Decode Ways.java Review Java [DP, String]

268 House Robber.java Easy Java [DP, Sequence DP]

269 House Robber II.java Medium Java [DP, Sequence DP]

270 Best Time to Buy and Sell Stock I.java Easy Java [Array, DP]

271 Best Time to Buy and Sell Stock II.java Easy Java [Array, Greedy]

272 Best Time to Buy and Sell Stock III .java Hard Java [Array, DP]

273 Best Time to Buy and Sell Stock IV.java Hard Java [DP]

274 Paint House II.java Review Java [DP]

275 3 Sum Smaller.java Medium Java [Array, Two Pointers]

276 Array Partition I.java Easy Java [Array]

277 1-bit and 2-bit Characters.java Easy Java [Array]

278 Non-decreasing Array.java Easy Java [Array]

279 Max Consecutive Ones.java Easy Java [Array]

280 Find All Numbers Disappeared in an Array.java Easy Java [Array]

281 Maximum Average Subarray I.java Easy Java [Array]

282 Largest Number At Least Twice of Others.java Easy Java [Array]

283 Toeplitz Matrix.java Easy Java [Array]

284 Backpack.java Medium Java [DP]

285 Sum of Two Integers.java Easy Java [Bit Manipulation]

286 Swap Bits.java Easy Java [Bit Manipulation]

287 Update Bits.java Medium Java [Bit Manipulation]

288 Maximum XOR of Two Numbers in an Array.java Medium Java [Bit Manipulation, Trie]

289 Perfect Squares.java Medium Java [BFS, DP, Math]

290 Palindrome Partitioning II.java Hard Java [DP]

291 Backpack V.java Medium Java [DP]

292 Backpack VI.java Medium Java [DP]

293 Copy Books.java Hard Java [Binary Search, DP]

294 Valid Perfect Square.java Review Java [Binary Search, Math]

295 Intersection of Two Arrays II.java Easy Java [Binary Search, Hash Table, Sort, Two Pointers]

296 Backpack II.java Medium Java [DP]

297 Backpack III.java Review Java [DP]

298 Longest Palindromic Subsequence.java Medium Java [DP]

299 Burst Balloons.java Hard Java [DP, Divide and Conquer]

300 Scramble String.java Hard Java [DP, String]

301 Binary Search Tree Iterator.java Medium Java [Design, Stack, Tree]

302 Flatten Nested List Iterator.java Medium Java [Design, Stack]

303 Best Time to Buy and Sell Stock with Cooldown.java Medium Java [DP]

304 Find Peak Element.java Medium Java [Array, Binary Search]

305 Longest Common Subsequence.java Medium Java [DP]

306 Interleaving String.java Hard Java [DP, String]

307 Letter Combinations of a Phone Number.java Medium Java [Backtracking, String]

308 Edit Distance.java Hard Java [DP, String]

309 Distinct Subsequences.java Hard Java [DP, String]

310 Regular Expression Matching.java Review Java [Backtracking, DP, String]

311 Majority Element.java Easy Java [Array, Bit Manipulation, Divide and Conquer]

312 Wildcard Matching.java Hard Java [Backtracking, DP, Greedy, String]

313 Ones and Zeroes.java Hard Java [DP]

314 Pow(x,n).java Medium Java [Binary Search, Math]

315 Word Break II.java Review Java [Backtracking, DP]

316 Nested List Weight Sum.java Easy Java [DFS]

317 Same Tree.java Easy Java [DFS, Tree]

318 Convert Sorted Array to Binary Search Tree.java Easy Java [DFS, Tree]

319 Binary Tree Maximum Path Sum.java Review Java [DFS, Tree]

320 Construct Binary Tree from Inorder and Preorder Traversal.java Medium Java [Array, DFS, Tree]

321 Path Sum.java Easy Java [DFS, Tree]

322 Add Binary.java Easy Java [Math, String]

323 Add Digits.java Easy Java [Math]

324 Add Two Numbers.java Medium Java [Linked List, Math]

325 Add Two Numbers II.java Medium Java [Linked List]

326 Balanced Binary Tree.java Medium Java [DFS, Tree]

327 Valid Anagram.java Easy Java [Hash Table, Sort]

328 Populating Next Right Pointers in Each Node.java Medium Java [DFS, Tree]

329 Validate Binary Search Tree.java Medium Java [DFS, Tree]

330 Convert Sorted List to Binary Search Tree.java Medium Java [DFS, Linked List]

331 Flatten Binary Tree to Linked List.java Medium Java [Binary Tree, DFS]

332 Binary Tree Paths.java Easy Java [Binary Tree, DFS]

333 Minimum Size Subarray Sum.java Medium Java [Array, Binary Search, Two Pointers]

334 Clone Graph.java Medium Java [BFS, DFS, Graph]

335 Longest Substring Without Repeating Characters.java Medium Java [Hash Table, String, Two Pointers]

336 Minimum Window Substring.java Hard Java [Hash Table, String, Two Pointers]

337 Linked List Cycle.java Easy Java [Linked List, Two Pointers]

338 Remove Nth Node From End of List.java Medium Java [Linked List, Two Pointers]

339 Longest Substring with At Most K Distinct Characters.java Medium Java [Hash Table, String]

340 Linked List Cycle II.java Medium Java [Linked List, Two Pointers]

341 Kth Smallest Number in Sorted Matrix.java Medium Java [Binary Search, Heap]

342 Find Minimum in Rotated Sorted Array.java Medium Java [Array, Binary Search]

343 Find Minimum in Rotated Sorted Array II.java Hard Java [Array, Binary Search]

344 Connecting Graph.java Medium Java [Union Find]

345 Connecting Graph II.java Medium Java [Union Find]

346 Connecting Graph III.java Medium Java [Union Find]

347 Number of Islands.java Medium Java [BFS, DFS, Union Find]

348 Number of Islands II.java Hard Java [Union Find]

349 Graph Valid Tree.java Medium Java [BFS, DFS, Graph, Union Find]

350 Surrounded Regions.java Review Java [BFS, DFS, Union Find]

351 Implement Trie.java Medium Java [Design, Trie]

352 Add and Search Word.java Medium Java [Backtracking, Design, Trie]

353 Word Search II.java Hard Java [Backtracking, DFS, Trie]

354 Word Search.java Medium Java [Array, Backtracking]

355 Word Squares.java Hard Java [Backtracking, Trie]

356 Trapping Rain Water.java Hard Java [Array, Stack, Two Pointers]

357 Trapping Rain Water II.java Hard Java [BFS, Heap]

358 Data Stream Median.java Hard Java [Design, Heap]

359 Sliding Window Median.java Hard Java [Design, Heap]

360 Min Stack.java Easy Java [Design, Stack]

361 Implement Queue using Stacks.java Easy Java [Design, Stack]

362 Expression Expand.java Medium Java [DFS, Divide and Conquer, Stack]

363 Largest Rectangle in Histogram.java Hard Java [Array, Stack]

364 Max Tree.java Medium Java [Stack, Tree]

365 Reverse Integer.java Easy Java [Math]

366 Swap Nodes in Pairs.java Medium Java [Linked List]

367 Find Peak Element II.java Hard Java [Binary Search, DFS, Divide and Conquer]

368 Sqrt(x).java Easy Java [Binary Search, Math]

369 First Bad Version.java Easy Java [Binary Search]

370 Wood Cut.java Medium Java [Binary Search]

371 Find the Duplicate Number.java Medium Java [Array, Binary Search, Two Pointers]

372 Palindrome Pairs.java Hard Java [Hash Table, String, Trie]

373 Game of Life.java Medium Java [Array]

374 Maximum Average Subarray II.java Review Java [Array, Binary Search]

375 Meeting Rooms.java Easy Java [Sort, Sweep Line]

376 Number of Airplane in the sky.java Medium Java [Array, Interval, Sort, Sweep Line]

377 Meeting Rooms II.java Medium Java [Greedy, Heap, Sort, Sweep Line]

378 Building Outline.java Review Java [Binary Indexed Tree, Divide and Conquer, Heap, Segment Tree, Sweep Line]

379 Unique Path.java Medium Java [Array, Coordinate DP, DP]

380 Maximal Rectangle.java Hard Java [Array, DP, Hash Table, Stack]

381 Maximal Square.java Medium Java [Coordinate DP, DP]

382 Minimum Path Sum.java Medium Java [Array, Coordinate DP, DP]

383 House Robber III.java Hard Java [DFS, DP, Status DP, Tree]

384 Longest Increasing Path in a Matrix.java Hard Java [DFS, DP, Memoization, Topological Sort]

385 Coins in a Line.java Medium Java [DP, Game Theory, Greedy]

386 Coins in a Line II.java Medium Java [Array, DP, Game Theory, Memoization, MiniMax]

387 Binary Tree Inorder Traversal.java Easy Java [Hash Table, Stack, Tree]

388 Path Sum II.java Easy Java [DFS, Tree]

389 Binary Tree Postorder Traversal.java Medium Java [Stack, Tree, Two Stacks]

390 Change to Anagram.java Easy Java [String]

391 Classical Binary Search.java Easy Java [Binary Search]

392 Climbing Stairs.java Easy Java [DP, Memoization, Sequence DP]

393 Coins in a Line III.java Hard Java [Array, DP, Game Theory, Interval DP, Memoization]

394 Closest Binary Search Tree Value.java Easy Java [Binary Search, Tree]

395 Compare Version Numbers.java Medium Java [String]

396 Count Complete Tree Nodes.java Medium Java [Binary Search, Tree]

397 Course Schedule.java Medium Java [BFS, DFS, Graph, Topological Sort]

398 Course Schedule II.java Medium Java [BFS, DFS, Graph, Topological Sort]