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

借此机会, 正式介绍一下自己, 以及我背后的大老板

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	Video Tutorial
0	2 Sum II - Input array is sorted.java	Medium	Java
1	2 Sum II.java	Medium	Java
2	2 Sum.java	Medium	Java	Link
3	3 Sum Closest.java	Medium	Java
4	3 Sum Smaller.java		Java
5	3 Sum.java	Medium	Java
6	4 Sum.java	Medium	Java
7	A+B.java	Easy	Java
8	Add and Search Word.java	Medium	Java
9	Add Binary.java	Easy	Java
10	Add Digits.java	Easy	Java
11	Add Two Numbers II.java	Medium	Java
12	Add Two Numbers.java	Easy	Java
13	Alien Dictionary.java	Hard	Java
14	Anagrams.java	Medium	Java
15	Array Partition I.java	Easy	Java
16	Backpack II.java	Medium	Java
17	Backpack.java	Medium	Java
18	Balanced Binary Tree.java	Medium	Java
19	Best Time to Buy and Sell Stock I.java	Easy	Java
20	Best Time to Buy and Sell Stock II.java	Easy	Java
21	Best Time to Buy and Sell Stock III .java	Medium	Java
22	Best Time to Buy and Sell Stock IV.java	Hard	Java
23	Binary Representation.java	Hard	Java
24	Binary Search Tree Iterator.java	Hard	Java
25	Binary Tree Inorder Traversal.java	Easy	Java
26	Binary Tree Level Order Traversal II.java	Medium	Java
27	Binary Tree Level Order Traversal.java	Medium	Java
28	Binary Tree Longest Consecutive Sequence.java	Medium	Java
29	Binary Tree Maximum Path Sum II.java	Medium	Java
30	Binary Tree Maximum Path Sum.java	Medium	Java
31	Binary Tree Path Sum.java	Easy	Java
32	Binary Tree Paths.java	Easy	Java
33	Binary Tree Postorder Traversal.java	Easy	Java
34	Binary Tree Preorder Traversal.java	Easy	Java
35	Binary Tree Right Side View.java	Medium	Java
36	Binary Tree Serialization.java	Medium	Java
37	Binary Tree Zigzag Level Order Traversal.java	Medium	Java
38	Building Outline.java	Hard	Java
39	Burst Balloons.java		Java
40	Change to Anagram.java	Easy	Java
41	Classical Binary Search.java	Easy	Java
42	Climbing Stairs.java	Easy	Java
43	Clone Graph.java	Medium	Java
44	Closest Binary Search Tree Value.java	Easy	Java
45	Closest Number in Sorted Array.java	Easy	Java
46	Coins in a Line.java		Java
47	ColorGrid.java	Medium	Java
48	Combination Sum II.java	Medium	Java
49	Combination Sum.java	Medium	Java
50	Combinations.java	Medium	Java
51	Compare Strings.java	Easy	Java
52	Complete Binary Tree.java	Easy	Java
53	Construct Binary Tree from Inorder and Postorder Traversal.java	Medium	Java
54	Construct Binary Tree from Inorder and Preorder Traversal.java	Medium	Java
55	Container With Most Water.java		Java
56	Contains Duplicate II.java	Easy	Java
57	Contains Duplicate III.java	Medium	Java
58	Contains Duplicate.java	Easy	Java
59	Convert Binary Search Tree to Doubly Linked List.java	Medium	Java
60	Convert Expression to Polish Notation.java	Hard	Java
61	Convert Expression to Reverse Polish Notation.java	Hard	Java
62	Convert Integer A to Integer B.java	Easy	Java
63	Convert Sorted Array to Binary Search Tree With Minimal Height.java	Easy	Java
64	Convert Sorted List to Binary Search Tree.java	Medium	Java
65	Copy List with Random Pointer.java	Medium	Java
66	Cosine Similarity.java	Easy	Java
67	Count 1 in Binary.java	Easy	Java
68	Count and Say.java	Easy	Java
69	Count of Smaller Number before itself.java	Hard	Java
70	Count of Smaller Number.java	Medium	Java
71	Count Primes.java	Easy	Java
72	Course Schedule II.java	Medium	Java
73	Course Schedule.java	Medium	Java
74	Data Stream Median.java	Hard	Java
75	Delete Digits.java	Medium	Java
76	Delete Node in the Middle of Singly Linked List.java	Easy	Java
77	Distinct Subsequences.java	Hard	Java
78	Edit Distance.java	Medium	Java
79	Encode and Decode Strings.java	Medium	Java
80	ExcelSheetColumnNumber .java	Easy	Java
81	Expression Evaluation.java	Hard	Java
82	Expression Tree Build.java	Hard	Java
83	Fast Power.java	Medium	Java
84	Fibonacci.java	Easy	Java
85	Find All Numbers Disappeared in an Array.java	Easy	Java
86	Find Minimum in Rotated Sorted Array II.java		Java
87	Find Minimum in Rotated Sorted Array.java		Java
88	Find Peak Element II.java		Java
89	Find Peak Element.java		Java
90	Find the Connected Component in the Undirected Graph.java	Medium	Java
91	Find the Weak Connected Component in the Directed Graph.java	Medium	Java
92	First Bad Version.java	Medium	Java
93	First Missing Positive.java		Java
94	Flatten 2D Vector.java		Java
95	Flatten Binary Tree to Linked List.java	Easy	Java
96	Flattern 2D Vector.java		Java
97	Flip Game II.java		Java
98	Flip Game.java		Java
99	Fraction to Recurring Decimal.java		Java
100	Game of Life.java		Java
101	Gas Station.java		Java
102	Generate Parentheses.java	Medium	Java
103	Graph Valid Tree.java	Medium	Java
104	Gray Code.java	Medium	Java
105	Group Anagrams.java	Medium	Java
106	Group Shifted Strings.java	Easy	Java
107	H-Index II.java		Java
108	H-Index.java		Java
109	Hamming Distance.java	Easy	Java
110	Happy Number.java	Easy	Java
111	Hash Function.java	Easy	Java
112	HashHeap.java	Hard	Java
113	HashWithArray.java	Easy	Java
114	HashWithCustomizedClass(LinkedList).java	Medium	Java
115	Heapify.java	Medium	Java
116	Heaters.java	Easy	Java
117	House Robber II.java	Medium	Java
118	House Robber III.java	Hard	Java
119	House Robber.java	Easy	Java
120	Identical Binary Tree.java	Easy	Java
121	Implement Queue by Two Stacks.java		Java
122	Implement Queue using Stacks.java	Easy	Java
123	Implement Stack by Two Queues.java		Java
124	Implement Stack using Queues.java	Easy	Java
125	Implement Stack.java		Java
126	Implement strStr().java		Java
127	Implement Trie (Prefix Tree).java		Java
128	Implement Trie.java	Medium	Java
129	IndexMatch.java	Easy	Java
130	Inorder Successor in Binary Search Tree.java	Medium	Java
131	Insert Interval.java	Easy	Java
132	Insert Node in a Binary Search Tree .java	Easy	Java
133	Insertion Sort List.java		Java
134	Integer to English Words.java		Java
135	Interleaving Positive and Negative Numbers.java		Java
136	Interleaving String.java		Java
137	Intersection of Two Arrays.java	Easy	Java
138	Intersection of Two Linked Lists.java	Easy	Java
139	Interval Minimum Number.java	Medium	Java
140	Interval Sum II.java	Hard	Java
141	Interval Sum.java	Medium	Java
142	Invert Binary Tree.java	Easy	Java
143	Isomorphic Strings.java	Easy	Java
144	Jump Game II.java	Hard	Java
145	Jump Game.java	Medium	Java
146	Kth Largest Element.java	Medium	Java
147	Kth Smallest Element in a BST.java		Java
148	Kth Smallest Number in Sorted Matrix.java	Medium	Java
149	Kth Smallest Sum In Two Sorted Arrays.java	Hard	Java
150	Largest Number.java		Java
151	Largest Rectangle in Histogram.java		Java
152	Last Position of Target.java		Java
153	Length of Last Word.java		Java
154	Letter Combinations of a Phone Number.java	Medium	Java
155	Linked List Cycle II.java		Java
156	Linked List Cycle.java		Java
157	Longest Common Prefix.java	Medium	Java
158	Longest Common Subsequence.java		Java
159	Longest Common Substring.java		Java
160	Longest Consecutive Sequence.java		Java
161	Longest Increasing Continuous subsequence II.java		Java
162	Longest Increasing Continuous subsequence.java		Java
163	Longest Increasing Subsequence.java		Java
164	Longest Palindromic Substring.java	Medium	Java
165	Longest Substring with At Most K Distinct Characters.java	Medium	Java
166	Longest Substring Without Repeating Characters.java	Medium	Java
167	Longest Univalue Path.java	Easy	Java
168	Longest Words.java		Java
169	Lowest Common Ancestor II.java	Easy	Java
170	Lowest Common Ancestor of a Binary Search Tree.java	Medium	Java
171	Lowest Common Ancestor.java	Easy	Java
172	LRU Cache.java	Hard	Java
173	Majority Number II.java	Medium	Java
174	Majority Number III.java	Medium	Java
175	Majority Number.java	Easy	Java
176	Matrix Zigzag Traversal.java	Easy	Java
177	Max Area of Island.java	Easy	Java
178	Max Consecutive Ones.java	Easy	Java
179	Max Tree.java	Hard	Java
180	Maximal Square.java	Medium	Java
181	Maximum Depth of Binary Tree.java	Easy	Java
182	Maximum Product Subarray.java		Java
183	Maximum Subarray III.java		Java
184	Maximum Subarray.java		Java
185	Maximum SubarrayII.java		Java
186	MaximumSubarray.java		Java
187	MaximumSubarrayII.java		Java
188	Median of two Sorted Arrays.java	Hard	Java
189	Median.java		Java
190	Meeting Rooms II.java	Medium	Java
191	Meeting Rooms.java	Easy	Java
192	Merge Intervals.java	Easy	Java
193	Merge k Sorted Arrays.java	Medium	Java
194	Merge k Sorted Lists.java	Medium	Java
195	Merge Sorted Array II.java		Java
196	Merge Sorted Array.java	Easy	Java
197	Merge Two Binary Trees.java	Easy	Java
198	Merge Two Sorted List.java	Easy	Java
199	Merge Two Sorted Lists.java	Easy	Java
200	Middle of Linked List.java		Java
201	Min Stack.java	Easy	Java
202	Minimum Absolute Difference in BST.java	Easy	Java
203	Minimum Height Trees.java		Java
204	Minimum Path Sum.java		Java
205	Minimum Size Subarray Sum.java	Medium	Java
206	Minimum Subarray.java		Java
207	Minimum Window Substring.java	Hard	Java
208	MinimumDepthOfBinaryTree.java	Easy	Java
209	Missing Ranges.java		Java
210	Multiply Strings.java	Medium	Java
211	Next Permutation.java	Medium	Java
212	Nim Game.java		Java
213	NQueens.java		Java
214	NQueensII.java		Java
215	Nth to Last Node in List.java		Java
216	Number of Airplane in the sky.java	Medium	Java
217	Number of Islands II.java	Hard	Java
218	Number of Islands.java	Medium	Java
219	Number Triangles.java		Java
220	O(1) Check Power of 2.java		Java
221	One Edit Distance.java	Medium	Java
222	Paint Fence.java		Java
223	Palindrome Linked List.java		Java
224	Palindrome Partitioning II.java		Java
225	Palindrome Partitioning.java		Java
226	Palindrome Permutation II.java	Medium	Java
227	Palindrome Permutation.java	Easy	Java
228	Partition Array by Odd and Even.java		Java
229	Partition Array.java		Java
230	Partition List.java		Java
231	Pascal's Triangle II.java	Easy	Java
232	Peeking Iterator.java		Java
233	Perfect Squares.java		Java
234	Permutation Index.java	Easy	Java
235	Permutation Sequence.java	Medium	Java
236	Permutations II.java	Medium	Java
237	Permutations.java	Medium	Java
238	Plus One.java		Java
239	Populating Next Right Pointers in Each Node II.java	Hard	Java
240	Populating Next Right Pointers in Each Node.java	Medium	Java
241	Pow(x,n).java		Java
242	Power of Three.java	Easy	Java
243	Product of Array Exclude Itself.java		Java
244	QuickSort.java	Easy	Java
245	Recover Rotated Sorted Array.java		Java
246	Rehashing.java	Medium	Java
247	Remove Duplicates from Sorted Array.java	Easy	Java
248	Remove Duplicates from Sorted List II.java		Java
249	Remove Duplicates from Sorted List.java	Easy	Java
250	Remove Duplicates from Unsorted List.java		Java
251	Remove Linked List Elements.java		Java
252	Remove Node in Binary Search Tree.java	Hard	Java
253	Remove Nth Node From End of List.java		Java
254	Reorder List.java		Java
255	Reshape the Matrix.java	Easy	Java
256	Restore IP Addresses.java		Java
257	Reverse Integer.java	Easy	Java
258	Reverse Linked List II .java		Java
259	Reverse Linked List.java	Easy	Java
260	Reverse String.java	Easy	Java
261	Reverse Words in a String II.java	Medium	Java
262	Reverse Words in a String.java	Medium	Java
263	reverseInteger.java		Java
264	Roman to Integer.java	Easy	Java
265	Rotate Image.java	Medium	Java
266	Rotate List.java		Java
267	Rotate String.java		Java
268	Search a 2D Matrix II.java		Java
269	Search a 2D Matrix.java		Java
270	Search for a Range.java		Java
271	Search Insert Position.java		Java
272	Search Range in Binary Search Tree .java	Medium	Java
273	Search Rotated in Sorted Array II.java		Java
274	Search Rotated in Sorted Array.java	Hard	Java
275	Segment Tree Build II.java	Medium	Java
276	Segment Tree Build.java	Medium	Java
277	Segment Tree Modify.java	Medium	Java
278	Segment Tree Query II.java	Medium	Java
279	Segment Tree Query.java	Medium	Java
280	Serilization and Deserialization Of Binary Tree.java		Java
281	Shortest Word Distance.java	Easy	Java
282	Single Number II.java		Java
283	Single Number III.java		Java
284	Single Number.java	Easy	Java
285	Singleton.java		Java
286	Sliding Window Maximum.java		Java
287	Sliding Window Median.java		Java
288	Sort Color.java		Java
289	Sort Colors II.java		Java
290	Sort Letters by Case.java		Java
291	Sort List.java		Java
292	Space Replacement.java		Java
293	Sqrt(x).java	Easy	Java
294	Stone Game.java		Java
295	String Permutation.java	Easy	Java
296	String to Integer(atoi).java	Easy	Java
297	Strobogrammatic Number II.java	Medium	Java
298	Strobogrammatic Number.java	Easy	Java
299	StrStr.java		Java
300	Subarray Sum Closest.java	Medium	Java
301	Subarray Sum.java	Easy	Java
302	Subset.java	Medium	Java
303	Subsets II.java	Medium	Java
304	Subtree.java	Easy	Java
305	Summary Ranges.java		Java
306	Surrounded Regions.java		Java
307	Swap Nodes in Pairs.java		Java
308	Symmetric Binary Tree.java	Easy	Java
309	The Smallest Difference.java		Java
310	Top K Frequent Elements.java	Medium	Java
311	Top K Frequent Words.java	Medium	Java
312	Topological Sorting.java	Medium	Java
313	Total Occurrence of Target.java		Java
314	Trailing Zeros.java		Java
315	Trapping Rain Water II.java	Hard	Java
316	Trapping Rain Water.java	Medium	Java
317	Triangle Count.java		Java
318	Tweaked Identical Binary Tree.java	Easy	Java
319	Two Lists Sum.java		Java
320	Two Strings Are Anagrams.java	Easy	Java
321	Ugly Number II.java		Java
322	Ugly Number.java	Medium	Java
323	Unique Binary Search Tree II.java		Java
324	Unique Binary Search Tree.java		Java
325	Unique Characters.java		Java
326	Unique Path.java	Medium	Java
327	Unique Paths II.java		Java
328	Unique Word Abbreviation.java		Java
329	Update Bits.java		Java
330	Valid Anagram.java	Easy	Java
331	Valid Palindrome.java	Easy	Java	Link
332	Valid Parentheses.java	Easy	Java
333	Valid Sudoku.java	Easy	Java
334	Validate Binary Search Tree.java	Medium	Java
335	Wiggle Sort.java		Java
336	Wood Cut.java		Java
337	Word Break II.java	Hard	Java
338	Word Break.java	Medium	Java
339	Word Ladder II.java	Hard	Java
340	Word Ladder.java	Medium	Java
341	Word Pattern.java	Easy	Java
342	Word Search II.java	Hard	Java
343	Word Search.java	Medium	Java
344	Zigzag Iterator.java		Java