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