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