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(wangdeve@gmail.com), 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 Inorder Traversal.java	Easy	Java	[]
4	Binary Tree Level Order Traversal II.java	Medium	Java	[]
5	Binary Tree Level Order Traversal.java	Medium	Java	[]
6	Binary Tree Longest Consecutive Sequence.java	Medium	Java	[]
7	Binary Tree Maximum Path Sum II.java	Medium	Java	[]
8	Binary Tree Path Sum.java	Easy	Java	[]
9	Binary Tree Postorder Traversal.java	Easy	Java	[]
10	Binary Tree Preorder Traversal.java	Easy	Java	[]
11	Binary Tree Right Side View.java	Medium	Java	[]
12	Binary Tree Serialization.java	Medium	Java	[]
13	Binary Tree Zigzag Level Order Traversal.java	Medium	Java	[]
14	Building Outline.java	Hard	Java	[]
15	Change to Anagram.java	Easy	Java	[]
16	Classical Binary Search.java	Easy	Java	[]
17	Climbing Stairs.java	Easy	Java	[]
18	Closest Binary Search Tree Value.java	Easy	Java	[]
19	Closest Number in Sorted Array.java	Easy	Java	[]
20	ColorGrid.java	Medium	Java	[]
21	Combination Sum II.java	Medium	Java	[]
22	Combination Sum.java	Medium	Java	[]
23	Combinations.java	Medium	Java	[]
24	Compare Strings.java	Easy	Java	[]
25	Complete Binary Tree.java	Easy	Java	[]
26	Construct Binary Tree from Inorder and Postorder Traversal.java	Medium	Java	[]
27	Container With Most Water.java	Medium	Java	[]
28	Contains Duplicate II.java	Easy	Java	[]
29	Contains Duplicate III.java	Medium	Java	[]
30	Contains Duplicate.java	Easy	Java	[]
31	Convert Binary Search Tree to Doubly Linked List.java	Medium	Java	[]
32	Convert Expression to Polish Notation.java	Hard	Java	[]
33	Convert Expression to Reverse Polish Notation.java	Hard	Java	[]
34	Convert Integer A to Integer B.java	Easy	Java	[]
35	Copy List with Random Pointer.java	Medium	Java	[]
36	Cosine Similarity.java	Easy	Java	[]
37	Count 1 in Binary.java	Easy	Java	[]
38	Count and Say.java	Easy	Java	[]
39	Count of Smaller Number before itself.java	Hard	Java	[]
40	Count of Smaller Number.java	Medium	Java	[]
41	Count Primes.java	Easy	Java	[]
42	Course Schedule II.java	Medium	Java	[]
43	Course Schedule.java	Medium	Java	[]
44	Data Stream Median.java	Hard	Java	[]
45	Delete Digits.java	Medium	Java	[]
46	Delete Node in the Middle of Singly Linked List.java	Easy	Java	[]
47	Encode and Decode Strings.java	Medium	Java	[]
48	ExcelSheetColumnNumber .java	Easy	Java	[]
49	Expression Evaluation.java	Hard	Java	[]
50	Expression Tree Build.java	Hard	Java	[]
51	Fast Power.java	Medium	Java	[]
52	Fibonacci.java	Easy	Java	[]
53	Find Minimum in Rotated Sorted Array II.java	N/A	Java	[]
54	Find Minimum in Rotated Sorted Array.java	N/A	Java	[]
55	Find Peak Element II.java	N/A	Java	[]
56	Find the Connected Component in the Undirected Graph.java	Medium	Java	[]
57	Find the Weak Connected Component in the Directed Graph.java	Medium	Java	[]
58	First Missing Positive.java	N/A	Java	[]
59	Flatten 2D Vector.java	Medium	Java	[]
60	Flip Game II.java	Medium	Java	[]
61	Flip Game.java	Easy	Java	[]
62	Fraction to Recurring Decimal.java	Medium	Java	[]
63	Game of Life.java	N/A	Java	[]
64	Gas Station.java	N/A	Java	[]
65	Generate Parentheses.java	Medium	Java	[]
66	Graph Valid Tree.java	Medium	Java	[]
67	Gray Code.java	Medium	Java	[]
68	Group Anagrams.java	Medium	Java	[]
69	Group Shifted Strings.java	Easy	Java	[]
70	H-Index II.java	Medium	Java	[]
71	H-Index.java	Medium	Java	[]
72	Hamming Distance.java	Easy	Java	[]
73	Happy Number.java	Easy	Java	[]
74	Hash Function.java	Easy	Java	[]
75	HashHeap.java	Hard	Java	[]
76	HashWithArray.java	Easy	Java	[]
77	HashWithCustomizedClass(LinkedList).java	Medium	Java	[]
78	Heapify.java	Medium	Java	[]
79	Heaters.java	Easy	Java	[]
80	House Robber III.java	Hard	Java	[]
81	Identical Binary Tree.java	Easy	Java	[]
82	Implement Queue by Two Stacks.java	N/A	Java	[]
83	Implement Queue using Stacks.java	Easy	Java	[]
84	Implement Stack by Two Queues.java	Easy	Java	[]
85	Implement Stack using Queues.java	Easy	Java	[]
86	Implement Stack.java	Easy	Java	[]
87	Implement strStr().java	N/A	Java	[]
88	Implement Trie (Prefix Tree).java	Medium	Java	[]
89	Implement Trie.java	Medium	Java	[]
90	IndexMatch.java	Easy	Java	[]
91	Inorder Successor in Binary Search Tree.java	Medium	Java	[]
92	Insert Interval.java	Easy	Java	[]
93	Insert Node in a Binary Search Tree .java	Easy	Java	[]
94	Insertion Sort List.java	N/A	Java	[]
95	Integer to English Words.java	N/A	Java	[]
96	Interleaving Positive and Negative Numbers.java	N/A	Java	[]
97	Intersection of Two Arrays.java	Easy	Java	[]
98	Intersection of Two Linked Lists.java	Easy	Java	[]
99	Interval Minimum Number.java	Medium	Java	[]
100	Interval Sum II.java	Hard	Java	[]
101	Interval Sum.java	Medium	Java	[]
102	Invert Binary Tree.java	Easy	Java	[]
103	Isomorphic Strings.java	Easy	Java	[]
104	Jump Game II.java	Hard	Java	[]
105	Kth Largest Element.java	Medium	Java	[]
106	Kth Smallest Element in a BST.java	N/A	Java	[]
107	Kth Smallest Number in Sorted Matrix.java	Medium	Java	[]
108	Kth Smallest Sum In Two Sorted Arrays.java	Hard	Java	[]
109	Largest Number.java	N/A	Java	[]
110	Largest Rectangle in Histogram.java	N/A	Java	[]
111	Last Position of Target.java	N/A	Java	[]
112	Length of Last Word.java	N/A	Java	[]
113	Linked List Cycle II.java	N/A	Java	[]
114	Longest Common Prefix.java	Medium	Java	[]
115	Longest Common Substring.java	N/A	Java	[]
116	Longest Consecutive Sequence.java	N/A	Java	[]
117	Longest Increasing Continuous subsequence II.java	N/A	Java	[]
118	Longest Increasing Continuous subsequence.java	Easy	Java	[]
119	Longest Palindromic Substring.java	Medium	Java	[]
120	Longest Substring with At Most K Distinct Characters.java	Medium	Java	[]
121	Longest Univalue Path.java	Easy	Java	[]
122	Longest Word in Dictionary.java	Easy	Java	[]
123	Longest Words.java	N/A	Java	[]
124	Lowest Common Ancestor II.java	Easy	Java	[]
125	Lowest Common Ancestor of a Binary Search Tree.java	Medium	Java	[]
126	Lowest Common Ancestor.java	Easy	Java	[]
127	LRU Cache.java	Hard	Java	[]
128	Majority Number II.java	Medium	Java	[]
129	Majority Number III.java	Medium	Java	[]
130	Matrix Zigzag Traversal.java	Easy	Java	[]
131	Max Area of Island.java	Easy	Java	[]
132	Max Tree.java	Hard	Java	[]
133	Maximal Square.java	Medium	Java	[]
134	Maximum Average Subarray II.java	Review	Java	[]
135	Maximum Depth of Binary Tree.java	Easy	Java	[]
136	Maximum Subarray III.java	N/A	Java	[]
137	Maximum Subarray.java	Easy	Java	[]
138	Maximum SubarrayII.java	N/A	Java	[]
139	MaximumSubarrayII.java	N/A	Java	[]
140	Median of two Sorted Arrays.java	Hard	Java	[]
141	Median.java	N/A	Java	[]
142	Meeting Rooms II.java	Medium	Java	[]
143	Meeting Rooms.java	Easy	Java	[]
144	Merge Intervals.java	Easy	Java	[]
145	Merge k Sorted Arrays.java	Medium	Java	[]
146	Merge k Sorted Lists.java	Medium	Java	[]
147	Merge Sorted Array II.java	N/A	Java	[]
148	Merge Sorted Array.java	Easy	Java	[]
149	Merge Two Binary Trees.java	Easy	Java	[]
150	Merge Two Sorted Lists.java	Easy	Java	[]
151	Middle of Linked List.java	N/A	Java	[]
152	Min Stack.java	Easy	Java	[]
153	Minimum Absolute Difference in BST.java	Easy	Java	[]
154	Minimum Height Trees.java	N/A	Java	[]
155	Minimum Path Sum.java	N/A	Java	[]
156	Minimum Subarray.java	N/A	Java	[]
157	MinimumDepthOfBinaryTree.java	Easy	Java	[]
158	Missing Ranges.java	N/A	Java	[]
159	Multiply Strings.java	Medium	Java	[]
160	Next Permutation.java	Medium	Java	[]
161	Nim Game.java	Easy	Java	[]
162	NQueens.java	N/A	Java	[]
163	NQueensII.java	N/A	Java	[]
164	Nth to Last Node in List.java	N/A	Java	[]
165	Number of Airplane in the sky.java	Medium	Java	[]
166	Number of Islands II.java	Hard	Java	[]
167	Number of Islands.java	Medium	Java	[]
168	Number Triangles.java	N/A	Java	[]
169	O(1) Check Power of 2.java	N/A	Java	[]
170	One Edit Distance.java	Medium	Java	[]
171	Paint Fence.java	N/A	Java	[]
172	Palindrome Linked List.java	N/A	Java	[]
173	Palindrome Partitioning.java	N/A	Java	[]
174	Palindrome Permutation II.java	Medium	Java	[]
175	Palindrome Permutation.java	Easy	Java	[]
176	Partition Array by Odd and Even.java	N/A	Java	[]
177	Partition Array.java	N/A	Java	[]
178	Partition List.java	N/A	Java	[]
179	Pascal's Triangle II.java	Easy	Java	[]
180	Peeking Iterator.java	N/A	Java	[]
181	Permutation Index.java	Easy	Java	[]
182	Permutation Sequence.java	Medium	Java	[]
183	Permutations II.java	Medium	Java	[]
184	Permutations.java	Medium	Java	[]
185	Populating Next Right Pointers in Each Node II.java	Hard	Java	[]
186	Product of Array Exclude Itself.java	N/A	Java	[]
187	QuickSort.java	Easy	Java	[]
188	Recover Rotated Sorted Array.java	N/A	Java	[]
189	Rehashing.java	Medium	Java	[]
190	Remove Duplicates from Sorted Array.java	Easy	Java	[]
191	Remove Duplicates from Sorted List II.java	N/A	Java	[]
192	Remove Duplicates from Sorted List.java	Easy	Java	[]
193	Remove Duplicates from Unsorted List.java	N/A	Java	[]
194	Remove Invalid Parentheses.java	Hard	Java	[]
195	Remove Linked List Elements.java	N/A	Java	[]
196	Remove Node in Binary Search Tree.java	Hard	Java	[]
197	Reorder List.java	N/A	Java	[]
198	Reshape the Matrix.java	Easy	Java	[]
199	Restore IP Addresses.java	N/A	Java	[]
200	Reverse Integer.java	Easy	Java	[]
201	Reverse Linked List II .java	N/A	Java	[]
202	Reverse Linked List.java	Easy	Java	[]
203	Reverse String.java	Easy	Java	[]
204	Reverse Words in a String II.java	Medium	Java	[]
205	Reverse Words in a String.java	Medium	Java	[]
206	reverseInteger.java	Easy	Java	[]
207	Roman to Integer.java	Easy	Java	[]
208	Rotate Image.java	Medium	Java	[]
209	Rotate List.java	N/A	Java	[]
210	Rotate String.java	N/A	Java	[]
211	Russian Doll Envelopes.java	N/A	Java	[]
212	Search a 2D Matrix II.java	N/A	Java	[]
213	Search a 2D Matrix.java	N/A	Java	[]
214	Search for a Range.java	N/A	Java	[]
215	Search Insert Position.java	N/A	Java	[]
216	Search Range in Binary Search Tree .java	Medium	Java	[]
217	Search Rotated in Sorted Array II.java	N/A	Java	[]
218	Search Rotated in Sorted Array.java	Hard	Java	[]
219	Segment Tree Build II.java	Medium	Java	[]
220	Segment Tree Build.java	Medium	Java	[]
221	Segment Tree Modify.java	Medium	Java	[]
222	Segment Tree Query II.java	Medium	Java	[]
223	Segment Tree Query.java	Medium	Java	[]
224	Serilization and Deserialization Of Binary Tree.java	N/A	Java	[]
225	Shortest Word Distance.java	Easy	Java	[]
226	Single Number II.java	N/A	Java	[]
227	Single Number III.java	N/A	Java	[]
228	Single Number.java	Easy	Java	[]
229	Singleton.java	N/A	Java	[]
230	Sliding Window Maximum.java	N/A	Java	[]
231	Sliding Window Median.java	N/A	Java	[]
232	Sort Color.java	N/A	Java	[]
233	Sort Colors II.java	N/A	Java	[]
234	Sort Letters by Case.java	N/A	Java	[]
235	Sort List.java	N/A	Java	[]
236	Space Replacement.java	N/A	Java	[]
237	Sqrt(x).java	Easy	Java	[]
238	Stone Game.java	N/A	Java	[]
239	String Permutation.java	Easy	Java	[]
240	String to Integer(atoi).java	Easy	Java	[]
241	Strobogrammatic Number II.java	Medium	Java	[]
242	Strobogrammatic Number.java	Easy	Java	[]
243	StrStr.java	N/A	Java	[]
244	Subarray Sum Closest.java	Medium	Java	[]
245	Subarray Sum.java	Easy	Java	[]
246	Subset.java	Medium	Java	[]
247	Subsets II.java	Medium	Java	[]
248	Subtree.java	Easy	Java	[]
249	Summary Ranges.java	N/A	Java	[]
250	Surrounded Regions.java	N/A	Java	[]
251	Swap Nodes in Pairs.java	N/A	Java	[]
252	Symmetric Binary Tree.java	Easy	Java	[]
253	The Smallest Difference.java	N/A	Java	[]
254	Top K Frequent Elements.java	Medium	Java	[]
255	Top K Frequent Words.java	Medium	Java	[]
256	Topological Sorting.java	Medium	Java	[]
257	Total Occurrence of Target.java	N/A	Java	[]
258	Trailing Zeros.java	N/A	Java	[]
259	Trapping Rain Water II.java	Hard	Java	[]
260	Tweaked Identical Binary Tree.java	Easy	Java	[]
261	Two Lists Sum.java	N/A	Java	[]
262	Two Strings Are Anagrams.java	Easy	Java	[]
263	Ugly Number II.java	N/A	Java	[]
264	Ugly Number.java	Medium	Java	[]
265	Unique Binary Search Tree II.java	N/A	Java	[]
266	Unique Characters.java	N/A	Java	[]
267	Unique Word Abbreviation.java	N/A	Java	[]
268	Valid Palindrome.java	Easy	Java	[]
269	Valid Parentheses.java	Easy	Java	[]
270	Valid Sudoku.java	Easy	Java	[]
271	Wood Cut.java	N/A	Java	[]
272	Word Break.java	Medium	Java	[]
273	Word Ladder II.java	Hard	Java	[]
274	Word Ladder.java	Medium	Java	[]
275	Word Pattern.java	Easy	Java	[]
276	Word Search II.java	Hard	Java	[]
277	Word Search.java	Medium	Java	[]
278	Zigzag Iterator.java	N/A	Java	[]
279	Find Anagram Mappings.java	Easy	Java	[]
280	Judge Route Circle.java	Easy	Java	[]
281	Island Perimeter.java	Easy	Java	[]
282	First Unique Character in a String.java	Easy	Java	[]
283	Power of Three.java	Easy	Java	[]
284	Plus One.java	Easy	Java	[]
285	Power of Two.java	Easy	Java	[]
286	Reverse Vowels of a String.java	Easy	Java	[]
287	Guess Number Higher or Lower.java	Easy	Java	[]
288	Encode and Decode TinyURL.java	Medium	Java	[]
289	Wiggle Sort.java	Medium	Java	[]
290	Queue Reconstruction by Height.java	Medium	Java	[]
291	2 Sum.java	Easy	Java	[]	Link
292	2 Sum II - Input array is sorted.java	Medium	Java	[]
293	2 Sum II.java	Medium	Java	[]
294	Coin Change.java	Medium	Java	[]
295	Unique Path.java	Medium	Java	[]
296	Jump Game.java	Medium	Java	[]
297	Maximum Product Subarray.java	Medium	Java	[]
298	3 Sum Closest.java	Medium	Java	[]
299	Triangle Count.java	Medium	Java	[]
300	3 Sum.java	Medium	Java	[]
301	4 Sum.java	Medium	Java	[]
302	k Sum.java	Hard	Java	[]
303	Trapping Rain Water.java	Hard	Java	[]
304	Longest Continuous Increasing Subsequence.java	Easy	Java	[]
305	Longest Increasing Subsequence.java	Medium	Java	[]
306	Unique Binary Search Tree.java	Medium	Java	[]
307	Trim a Binary Search Tree.java	Easy	Java	[]
308	Unique Paths II.java	Medium	Java	[]
309	Counting Bits.java	Medium	Java	[]
310	Bomb Enemy.java	Medium	Java	[]
311	Paint House.java	Easy	Java	[]
312	Decode Ways.java	Review	Java	[]
313	House Robber.java	Easy	Java	[]
314	House Robber II.java	Medium	Java	[]
315	Best Time to Buy and Sell Stock I.java	Easy	Java	[]
316	Best Time to Buy and Sell Stock II.java	Easy	Java	[]
317	Best Time to Buy and Sell Stock III .java	Hard	Java	[]
318	Best Time to Buy and Sell Stock IV.java	Hard	Java	[]
319	Paint House II.java	Review	Java	[]
320	3 Sum Smaller.java	Medium	Java	[]
321	Array Partition I.java	Easy	Java	[]
322	1-bit and 2-bit Characters.java	Easy	Java	[]
323	Non-decreasing Array.java	Easy	Java	[]
324	Max Consecutive Ones.java	Easy	Java	[]
325	Find All Numbers Disappeared in an Array.java	Easy	Java	[]
326	Maximum Average Subarray I.java	Easy	Java	[]
327	Largest Number At Least Twice of Others.java	Easy	Java	[]
328	Toeplitz Matrix.java	Easy	Java	[]
329	Backpack.java	Medium	Java	[]
330	A+B.java	Easy	Java	[]
331	Swap Bits.java	Easy	Java	[]
332	Update Bits.java	Medium	Java	[]
333	Maximum XOR of Two Numbers in an Array.java	Medium	Java	[]
334	Coins in a Line.java	Medium	Java	[]
335	Perfect Squares.java	Medium	Java	[]
336	Palindrome Partitioning II.java	Hard	Java	[]
337	Backpack V.java	Medium	Java	[]
338	Backpack VI.java	Medium	Java	[]
339	Copy Books.java	Review	Java	[]
340	Valid Perfect Square.java	Review	Java	[]
341	Intersection of Two Arrays II.java	Easy	Java	[]
342	First Bad Version.java	Easy	Java	[]
343	Backpack II.java	Medium	Java	[]
344	Backpack III.java	Review	Java	[]
345	Longest Palindromic Subsequence.java	Medium	Java	[]
346	Burst Balloons.java	Hard	Java	[]
347	Scramble String.java	Hard	Java	[]
348	Binary Search Tree Iterator.java	Medium	Java	[]
349	Flatten Nested List Iterator.java	Medium	Java	[]
350	Coins in a Line III.java	Hard	Java	[]
351	Best Time to Buy and Sell Stock with Cooldown.java	Medium	Java	[]
352	Find Peak Element.java	Medium	Java	[]
353	Longest Common Subsequence.java	Medium	Java	[]
354	Interleaving String.java	Hard	Java	[]
355	Letter Combinations of a Phone Number.java	Medium	Java	[]
356	Edit Distance.java	Hard	Java	[]
357	Distinct Subsequences.java	Hard	Java	[]
358	Regular Expression Matching.java	Review	Java	[]
359	Majority Element.java	Easy	Java	[]
360	Wildcard Matching.java	Hard	Java	[]
361	Ones and Zeroes.java	Hard	Java	[]
362	Pow(x,n).java	Medium	Java	[]
363	Word Break II.java	Review	Java	[]
364	Nested List Weight Sum.java	Easy	Java	[]
365	Same Tree.java	Easy	Java	[]
366	Convert Sorted Array to Binary Search Tree.java	Easy	Java	[]
367	Binary Tree Maximum Path Sum.java	Review	Java	[]
368	Construct Binary Tree from Inorder and Preorder Traversal.java	Medium	Java	[]
369	Path Sum.java	Easy	Java	[]
370	Add and Search Word.java	Medium	Java	[]
371	Add Binary.java	Easy	Java	[]
372	Add Digits.java	Easy	Java	[]
373	Add Two Numbers.java	Medium	Java	[]
374	Add Two Numbers II.java	Medium	Java	[]
375	Balanced Binary Tree.java	Medium	Java	[]
376	Valid Anagram.java	Easy	Java	[]
377	Populating Next Right Pointers in Each Node.java	Medium	Java	[]
378	Validate Binary Search Tree.java	Medium	Java	[]
379	Convert Sorted List to Binary Search Tree.java	Medium	Java	[]
380	Flatten Binary Tree to Linked List.java	Medium	Java	[Binary Tree, DFS]
381	Binary Tree Paths.java	Easy	Java	[Binary Tree, DFS]
382	Minimum Size Subarray Sum.java	Medium	Java	[Array, Binary Search, Two Pointers]
383	Clone Graph.java	Medium	Java	[BFS, DFS, Graph]
384	Longest Substring Without Repeating Characters.java	Medium	Java	[Hash Table, String, Two Pointers]
385	Minimum Window Substring.java	Hard	Java	[Hash Table, String, Two Pointers]
386	Linked List Cycle.java	Easy	Java	[Linked List, Two Pointers]
387	Remove Nth Node From End of List.java	Medium	Java	[Linked List, Two Pointers]