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	Count of Smaller Number before itself.java	Hard	Java	[]
1	Evaluate Division.java	Medium	Java	[BFS, DFS, Graph, Union Find]
2	Fraction to Recurring Decimal.java	Medium	Java	[Hash Table, Math]
3	Gray Code.java	Medium	Java	[Backtracking]
4	Hamming Distance.java	Easy	Java	[]
5	Happy Number.java	Easy	Java	[]
6	HashWithArray.java	Easy	Java	[]
7	Heaters.java	Easy	Java	[]
8	IndexMatch.java	Easy	Java	[]
9	Insert Node in a Binary Search Tree .java	Easy	Java	[BST]
10	Jewels and Stones.java	Easy	Java	[Hash Table]
11	Kth Smallest Sum In Two Sorted Arrays.java	Hard	Java	[]
12	LFU Cache.java	Hard	Java	[Design, Hash Table]
13	Longest Univalue Path.java	Easy	Java	[]
14	Majority Number II.java	Medium	Java	[Enumeration, Greedy]
15	Majority Number III.java	Medium	Java	[Hash Table, Linked List]
16	Matrix Zigzag Traversal.java	Easy	Java	[]
17	Maximum Subarray III.java	Review	Java	[]
18	Minimum Absolute Difference in BST.java	Easy	Java	[BST]
19	Minimum Height Trees.java	Medium	Java	[BFS, Graph]
20	Missing Ranges.java	Medium	Java	[Array]
21	Next Permutation.java	Medium	Java	[Array]
22	O(1) Check Power of 2.java	Easy	Java	[Bit Manipulation]
23	Palindrome Permutation II.java	Medium	Java	[Backtracking, Permutation]
24	Partition Array by Odd and Even.java	Easy	Java	[Array, Two Pointers]
25	Pascal's Triangle II.java	Easy	Java	[]
26	Permutation Index.java	Easy	Java	[]
27	Permutation Sequence.java	Medium	Java	[Backtracking, Math]
28	Prefix and Suffix Search.java	Hard	Java	[Trie]
29	Product of Array Exclude Itself.java	Medium	Java	[Array]
30	Recover Rotated Sorted Array.java	Easy	Java	[Array]
31	Remove Duplicates from Unsorted List.java	Medium	Java	[Linked List]
32	Remove Node in Binary Search Tree.java	Hard	Java	[BST]
33	Reshape the Matrix.java	Easy	Java	[]
34	Reverse String.java	Easy	Java	[]
35	Rotate Image.java	Medium	Java	[Array, Enumeration]
36	Search in Rotated Sorted Array II.java	Medium	Java	[Array, Binary Search]
37	Search Insert Position.java	Easy	Java	[]
38	Shortest Word Distance.java	Easy	Java	[]
39	Single Number II.java	Medium	Java	[Bit Manipulation]
40	Single Number III.java	Medium	Java	[Bit Manipulation]
41	Single Number.java	Easy	Java	[]
42	Space Replacement.java	Medium	Java	[String]
43	Stone Game.java	Medium	Java	[DP]
44	String Permutation.java	Easy	Java	[]
45	Subarray Sum II.java	Hard	Java	[Array, Binary Search, Two Pointers]
46	The Smallest Difference.java	Medium	Java	[Array, Sort, Two Pointers]
47	Total Occurrence of Target.java	Medium	Java	[]
48	Trailing Zeros.java	Easy	Java	[Math]
49	Two Lists Sum.java	Medium	Java	[Linked List]
50	Two Strings Are Anagrams.java	Easy	Java	[]
51	Valid Sudoku.java	Easy	Java	[Enumeration, Hash Table]
52	Word Pattern.java	Easy	Java	[]
53	Zigzag Iterator.java	Medium	Java	[BST]
54	Find Anagram Mappings.java	Easy	Java	[Hash Table]
55	Judge Route Circle.java	Easy	Java	[String]
56	Island Perimeter.java	Easy	Java	[Hash Table]
57	Power of Three.java	Easy	Java	[Math]
58	Plus One.java	Easy	Java	[Array, Math]
59	Power of Two.java	Easy	Java	[Bit Manipulation, Math]
60	Reverse Vowels of a String.java	Easy	Java	[String, Two Pointers]
61	Guess Number Higher or Lower.java	Easy	Java	[Binary Search]
62	Encode and Decode TinyURL.java	Medium	Java	[Hash Table, Math]
63	Wiggle Sort.java	Medium	Java	[Array, Sort]
64	Queue Reconstruction by Height.java	Medium	Java	[Greedy]
65	Two Sum II - Input array is sorted.java	Medium	Java	[Array, Binary Search, Two Pointers]
66	2 Sum II.java	Medium	Java	[Array, Binary Search, Two Pointers]
67	Coin Change.java	Medium	Java	[Backpack DP, DP, Memoization]
68	Maximum Product Subarray.java	Medium	Java	[Array, DP, Subarray]
69	3 Sum Closest.java	Medium	Java	[Array, Two Pointers]
70	Triangle Count.java	Medium	Java	[Array]
71	3Sum.java	Medium	Java	[Array, Two Pointers]
72	k Sum.java	Hard	Java	[DP]
73	Unique Binary Search Tree.java	Medium	Java	[BST, DP, Tree]
74	Trim a Binary Search Tree.java	Easy	Java	[BST, Tree]
75	Unique Paths II.java	Medium	Java	[Array, Coordinate DP, DP]
76	Bomb Enemy.java	Medium	Java	[Coordinate DP, DP]
77	3Sum Smaller.java	Medium	Java	[Array, Two Pointers]
78	Array Partition I.java	Easy	Java	[Array]
79	1-bit and 2-bit Characters.java	Easy	Java	[Array]
80	Non-decreasing Array.java	Easy	Java	[Array]
81	Max Consecutive Ones.java	Easy	Java	[Array]
82	Find All Numbers Disappeared in an Array.java	Easy	Java	[Array]
83	Maximum Average Subarray I.java	Easy	Java	[Array, Subarray]
84	Largest Number At Least Twice of Others.java	Easy	Java	[Array]
85	Toeplitz Matrix.java	Easy	Java	[Array]
86	Sum of Two Integers.java	Easy	Java	[Bit Manipulation]
87	Swap Bits.java	Easy	Java	[Bit Manipulation]
88	Update Bits.java	Medium	Java	[Bit Manipulation]
89	Maximum XOR of Two Numbers in an Array.java	Medium	Java	[Bit Manipulation, Trie]
90	Perfect Squares.java	Medium	Java	[BFS, DP, Math, Partition DP]
91	Backpack VI.java	Medium	Java	[Backpack DP, DP]
92	Copy Books.java	Hard	Java	[Binary Search, DP, Partition DP]
93	Valid Perfect Square.java	Review	Java	[Binary Search, Math]
94	Intersection of Two Arrays II.java	Easy	Java	[Binary Search, Hash Table, Sort, Two Pointers]
95	Scramble String.java	Hard	Java	[DP, Interval DP, String]
96	Binary Search Tree Iterator.java	Medium	Java	[BST, Design, Stack, Tree]
97	Flatten Nested List Iterator.java	Medium	Java	[Design, Stack]
98	Best Time to Buy and Sell Stock with Cooldown.java	Medium	Java	[DP]
99	Find Peak Element.java	Medium	Java	[Array, Binary Search]
100	Longest Common Subsequence.java	Medium	Java	[DP, Double Sequence DP, Sequence DP]
101	Interleaving String.java	Hard	Java	[DP, String]
102	Letter Combinations of a Phone Number.java	Medium	Java	[Backtracking, String]
103	Edit Distance.java	Hard	Java	[DP, Double Sequence DP, Sequence DP, String]
104	Distinct Subsequences.java	Hard	Java	[DP, String]
105	Majority Element.java	Easy	Java	[Array, Bit Manipulation, Divide and Conquer]
106	Ones and Zeroes.java	Hard	Java	[DP]
107	Pow(x, n).java	Medium	Java	[Binary Search, Math]
108	Word Break II.java	Hard	Java	[Backtracking, DFS, DP, Hash Table, Memoization]
109	Nested List Weight Sum.java	Easy	Java	[BFS, DFS]
110	Same Tree.java	Easy	Java	[DFS, Tree]
111	Convert Sorted Array to Binary Search Tree.java	Easy	Java	[DFS, Divide and Conquer, Tree]
112	Construct Binary Tree from Preorder and Inorder Traversal.java	Medium	Java	[Array, DFS, Divide and Conquer, Hash Table, Tree]
113	Add Digits.java	Easy	Java	[Math]
114	Add Two Numbers.java	Medium	Java	[Linked List, Math]
115	Add Two Numbers II.java	Medium	Java	[Linked List]
116	Balanced Binary Tree.java	Medium	Java	[DFS, Tree]
117	Valid Anagram.java	Easy	Java	[Hash Table, Sort]
118	Populating Next Right Pointers in Each Node.java	Medium	Java	[DFS, Divide and Conquer, Tree]
119	Validate Binary Search Tree.java	Medium	Java	[BST, DFS, Divide and Conquer, Tree]
120	Convert Sorted List to Binary Search Tree.java	Medium	Java	[BST, DFS, Divide and Conquer, Linked List]
121	Flatten Binary Tree to Linked List.java	Medium	Java	[Binary Tree, DFS]
122	Binary Tree Paths.java	Easy	Java	[Backtracking, Binary Tree, DFS]
123	Minimum Size Subarray Sum.java	Medium	Java	[Array, Binary Search, Subarray, Two Pointers]
124	Longest Substring Without Repeating Characters.java	Medium	Java	[Hash Table, String, Two Pointers]
125	Minimum Window Substring.java	Hard	Java	[Hash Table, String, Two Pointers]
126	Linked List Cycle.java	Easy	Java	[Linked List, Two Pointers]
127	Remove Nth Node From End of List.java	Medium	Java	[Linked List, Two Pointers]
128	Longest Substring with At Most K Distinct Characters.java	Hard	Java	[Hash Table, Sliding Window, String]
129	Linked List Cycle II.java	Medium	Java	[Linked List, Math, Two Pointers]
130	Kth Smallest Element in a Sorted Matrix.java	Medium	Java	[Binary Search, Heap]
131	Find Minimum in Rotated Sorted Array.java	Medium	Java	[Array, Binary Search]
132	Find Minimum in Rotated Sorted Array II.java	Hard	Java	[Array, Binary Search]
133	Connecting Graph.java	Medium	Java	[Union Find]
134	Connecting Graph II.java	Medium	Java	[Union Find]
135	Connecting Graph III.java	Medium	Java	[Union Find]
136	Number of Islands.java	Medium	Java	[BFS, DFS, Matrix DFS, Union Find]
137	Number of Islands II.java	Hard	Java	[Union Find]
138	Surrounded Regions.java	Medium	Java	[BFS, DFS, Matrix DFS, Union Find]
139	Implement Trie (Prefix Tree).java	Medium	Java	[Design, Trie]
140	Add and Search Word - Data structure design.java	Medium	Java	[Backtracking, Design, Trie]
141	Word Search II.java	Hard	Java	[Backtracking, DFS, Trie]
142	Word Search.java	Medium	Java	[Array, Backtracking, DFS]
143	Word Squares.java	Hard	Java	[Backtracking, Trie]
144	Trapping Rain Water.java	Hard	Java	[Array, Stack, Two Pointers]
145	Min Stack.java	Easy	Java	[Design, Stack]
146	Implement Queue using Stacks.java	Easy	Java	[Design, Stack]
147	Decode String.java	Medium	Java	[DFS, Divide and Conquer, Stack]
148	Largest Rectangle in Histogram.java	Hard	Java	[Array, Monotonous Stack, Stack]
149	Maximum Binary Tree.java	Medium	Java	[Stack, Tree]
150	Reverse Integer.java	Easy	Java	[Math]
151	Swap Nodes in Pairs.java	Medium	Java	[Linked List]
152	Find Peak Element II.java	Hard	Java	[Binary Search, DFS, Divide and Conquer]
153	Sqrt(x).java	Easy	Java	[Binary Search, Math]
154	First Bad Version.java	Easy	Java	[Binary Search]
155	Wood Cut.java	Medium	Java	[Binary Search]
156	Find the Duplicate Number.java	Medium	Java	[Array, Binary Search, Two Pointers]
157	Palindrome Pairs.java	Hard	Java	[Hash Table, String, Trie]
158	Game of Life.java	Medium	Java	[Array]
159	Maximum Average Subarray II.java	Review	Java	[Array, Binary Search, PreSum]
160	Meeting Rooms.java	Easy	Java	[PriorityQueue, Sort, Sweep Line]
161	Number of Airplane in the sky.java	Medium	Java	[Array, Interval, PriorityQueue, Sort, Sweep Line]
162	Meeting Rooms II.java	Medium	Java	[Greedy, Heap, PriorityQueue, Sort, Sweep Line]
163	The Skyline Problem.java	Review	Java	[Binary Indexed Tree, Divide and Conquer, Heap, PriorityQueue, Segment Tree, Sweep Line]
164	Unique Path.java	Medium	Java	[Array, Coordinate DP, DP]
165	Maximal Rectangle.java	Hard	Java	[Array, DP, Hash Table, Stack]
166	Maximal Square.java	Medium	Java	[Coordinate DP, DP]
167	Longest Increasing Path in a Matrix.java	Hard	Java	[Coordinate DP, DFS, DP, Memoization, Topological Sort]
168	Coins in a Line.java	Medium	Java	[DP, Game Theory, Greedy]
169	Coins in a Line II.java	Medium	Java	[Array, DP, Game Theory, Memoization, MiniMax]
170	Binary Tree Inorder Traversal.java	Easy	Java	[Hash Table, Stack, Tree]
171	Binary Tree Postorder Traversal.java	Medium	Java	[Stack, Tree, Two Stacks]
172	Change to Anagram.java	Easy	Java	[String]
173	Classical Binary Search.java	Easy	Java	[Binary Search]
174	Climbing Stairs.java	Easy	Java	[DP, Memoization, Sequence DP]
175	Coins in a Line III.java	Hard	Java	[Array, DP, Game Theory, Interval DP, Memoization]
176	Closest Binary Search Tree Value.java	Easy	Java	[BST, Binary Search, Tree]
177	Compare Version Numbers.java	Medium	Java	[String]
178	Count Complete Tree Nodes.java	Medium	Java	[Binary Search, Tree]
179	Course Schedule.java	Medium	Java	[BFS, Backtracking, DFS, Graph, Topological Sort]
180	Course Schedule II.java	Medium	Java	[BFS, DFS, Graph, Topological Sort]
181	Binary Tree Preorder Traversal.java	Easy	Java	[BFS, DFS, Stack, Tree]
182	Closest Number in Sorted Array.java	Easy	Java	[Binary Search]
183	Complete Binary Tree.java	Easy	Java	[BFS, Tree]
184	Compare Strings.java	Easy	Java	[String]
185	Contains Duplicate.java	Easy	Java	[Array, Hash Table]
186	Contains Duplicate II.java	Easy	Java	[Array, Hash Table]
187	Contains Duplicate III.java	Medium	Java	[BST]
188	Burst Balloons.java	Hard	Java	[DP, Divide and Conquer, Interval DP, Memoization]
189	Nim Game.java	Easy	Java	[Brainteaser, DP, Game Theory]
190	Convert Integer A to Integer B.java	Easy	Java	[Bit Manipulation]
191	Cosine Similarity.java	Easy	Java	[Basic Implementation]
192	Count 1 in Binary.java	Easy	Java	[Bit Manipulation]
193	Count and Say.java	Easy	Java	[Basic Implementation, String]
194	K Edit Distance.java	Hard	Java	[DP, Double Sequence DP, Sequence DP, Trie]
195	Jump Game.java	Medium	Java	[Array, DP, Greedy]
196	Coin Change 2.java	Medium	Java	[Backpack DP, DP]
197	Paint House.java	Easy	Java	[DP, Sequence DP, Status DP]
198	Decode Ways.java	Medium	Java	[DP, Partition DP, String]
199	Longest Continuous Increasing Subsequence.java	Easy	Java	[Array, Coordinate DP, DP]
200	Minimum Path Sum.java	Medium	Java	[Array, Coordinate DP, DP]
201	Counting Bits.java	Medium	Java	[Bit Manipulation, Bitwise DP, DP]
202	Continuous Subarray Sum.java	Medium	Java	[Coordinate DP, DP, Math, Subarray]
203	House Robber.java	Easy	Java	[DP, Sequence DP]
204	House Robber II.java	Medium	Java	[DP, Sequence DP, Status DP]
205	House Robber III.java	Medium	Java	[DFS, DP, Status DP, Tree]
206	Paint House II.java	Hard	Java	[DP, Sequence DP, Status DP]
207	Best Time to Buy and Sell Stock III.java	Hard	Java	[Array, DP, Sequence DP]
208	Best Time to Buy and Sell Stock IV.java	Hard	Java	[DP, Sequence DP]
209	Russian Doll Envelopes.java	Hard	Java	[Binary Search, Coordinate DP, DP]
210	Permutation in String.java	Medium	Java	[Two Pointers]
211	Permutations II.java	Medium	Java	[Backtracking]
212	Shuffle an Array.java	Medium	Java	[Permutation]
213	Find All Anagrams in a String.java	Easy	Java	[Hash Table, Sliding Window]
214	Group Anagrams.java	Medium	Java	[Hash Table, String]
215	Backpack.java	Medium	Java	[Backpack DP, DP]
216	Backpack II.java	Medium	Java	[Backpack DP, DP]
217	Backpack V.java	Medium	Java	[Backpack DP, DP]
218	Count Primes.java	Easy	Java	[Hash Table, Math]
219	Delete Node in a Linked List.java	Easy	Java	[Linked List]
220	Excel Sheet Column Number.java	Easy	Java	[Math]
221	Excel Sheet Column Title.java	Easy	Java	[Math]
222	Flip Game.java	Easy	Java	[String]
223	Expression Tree Build.java	Hard	Java	[Binary Tree, Expression Tree, Minimum Binary Tree, Stack]
224	Expression Evaluation.java	Hard	Java	[Binary Tree, DFS, Expression Tree, Minimum Binary Tree, Stack]
225	Convert Expression to Polish Notation.java	Hard	Java	[Binary Tree, DFS, Expression Tree, Stack]
226	Convert Expression to Reverse Polish Notation.java	Hard	Java	[Binary Tree, DFS, Expression Tree, Stack]
227	Evaluate Reverse Polish Notation.java	Medium	Java	[Stack]
228	Decode Ways II.java	Hard	Java	[DP, Enumeration, Partition DP]
229	Palindrome Partitioning II.java	Hard	Java	[DP, Partition DP]
230	Backpack III.java	Hard	Java	[Backpack DP, DP]
231	First Missing Positive.java	Hard	Java	[Array]
232	Implement strStr().java	Easy	Java	[String, Two Pointers]
233	Insertion Sort List.java	Medium	Java	[Linked List, Sort]
234	Interleaving Positive and Negative Numbers.java	Medium	Java	[Two Pointers]
235	Largest Number.java	Medium	Java	[Sort]
236	Last Position of Target.java	Easy	Java	[Binary Search]
237	Length of Last Word.java	Easy	Java	[String]
238	Longest Common Substring.java	Medium	Java	[DP, Double Sequence DP, Sequence DP, String]
239	Longest Increasing Continuous subsequence.java	Easy	Java	[Array, Coordinate DP, DP]
240	Longest Increasing Continuous subsequence II.java	Medium	Java	[Array, Coordinate DP, DP, Memoization]
241	N-Queens.java	Hard	Java	[Backtracking]
242	N-Queens II.java	Hard	Java	[Backtracking]
243	Maximum Subarray.java	Easy	Java	[Array, DFS, DP, Divide and Conquer, PreSum, Sequence DP, Subarray]
244	Maximum Subarray II.java	Medium	Java	[Array, DP, Greedy, PreSum, Sequence DP, Subarray]
245	Median.java	Easy	Java	[Array, Quick Select, Quick Sort]
246	Middle of Linked List.java	Easy	Java	[Linked List]
247	Singleton.java	Easy	Java	[Design]
248	Remove Linked List Elements.java	Easy	Java	[Linked List]
249	Fibonacci.java	Easy	Java	[DP, Math, Memoization]
250	Palindrome Linked List.java	Easy	Java	[Linked List, Two Pointers]
251	Reverse Linked List.java	Easy	Java	[Linked List]
252	Reverse Linked List II .java	Medium	Java	[Linked List]
253	Intersection of Two Linked Lists.java	Easy	Java	[Linked List]
254	Palindrome Permutation.java	Easy	Java	[Hash Table]
255	Valid Palindrome.java	Easy	Java	[String, Two Pointers]
256	Implement Stack using Queues.java	Easy	Java	[Design, Stack]
257	Implement Stack.java	Easy	Java	[Stack]
258	Invert Binary Tree.java	Easy	Java	[BFS, DFS, Tree]
259	Maximum Depth of Binary Tree.java	Easy	Java	[DFS, Tree]
260	Minimum Depth of Binary Tree.java	Easy	Java	[BFS, DFS, Tree]
261	Symmetric Tree.java	Easy	Java	[BFS, DFS, Tree]
262	Tweaked Identical Binary Tree.java	Easy	Java	[DFS, Tree]
263	Merge Two Binary Trees.java	Easy	Java	[DFS, Tree]
264	Subtree.java	Easy	Java	[DFS, Tree]
265	Lowest Common Ancestor of a Binary Tree.java	Medium	Java	[DFS, Tree]
266	Lowest Common Ancestor II.java	Easy	Java	[Hash Table, Tree]
267	Lowest Common Ancestor of a Binary Search Tree.java	Medium	Java	[BST, DFS, Tree]
268	Hash Function.java	Easy	Java	[Hash Table]
269	Merge Two Sorted Lists.java	Easy	Java	[Linked List]
270	Missing Number.java	Easy	Java	[Array, Bit Manipulation, Math]
271	LRU Cache.java	Hard	Java	[Design, Hash Table, Linked List]
272	Remove Duplicates from Sorted Array.java	Easy	Java	[Array, Two Pointers]
273	Remove Duplicates from Sorted Array II.java	Medium	Java	[Array, Two Pointers]
274	Remove Duplicates from Sorted List.java	Easy	Java	[Linked List]
275	Remove Duplicates from Sorted List II.java	Medium	Java	[Linked List]
276	QuickSort.java	Medium	Java	[Quick Sort, Sort]
277	MergeSort.java	Medium	Java	[Merge Sort, Sort]
278	Longest Word in Dictionary.java	Easy	Java	[Hash Table, Trie]
279	Binary Tree Level Order Traversal.java	Medium	Java	[BFS, DFS, Tree]
280	Binary Tree Level Order Traversal II.java	Medium	Java	[BFS, Tree]
281	Binary Tree Longest Consecutive Sequence II.java	Medium	Java	[DFS, Divide and Conquer, Double Recursive, Tree]
282	Binary Tree Maximum Path Sum.java	Hard	Java	[DFS, DP, Tree, Tree DP]
283	Path Sum.java	Easy	Java	[DFS, Tree]
284	Path Sum II.java	Easy	Java	[Backtracking, DFS, Tree]
285	Path Sum III.java	Easy	Java	[DFS, Double Recursive, Tree]
286	Rotate String.java	Easy	Java	[String]
287	Combinations.java	Medium	Java	[Backtracking, Combination, DFS]
288	Combination Sum IV.java	Medium	Java	[Array, Backpack DP, DP]
289	Binary Tree Right Side View.java	Medium	Java	[BFS, DFS, Tree]
290	Binary Tree Maximum Path Sum II.java	Medium	Java	[DFS, Tree]
291	Rotate List.java	Medium	Java	[Linked List, Two Pointers]
292	Basic Calculator.java	Hard	Java	[Binary Tree, Expression Tree, Math, Minimum Binary Tree, Stack]
293	Longest Consecutive Sequence.java	Hard	Java	[Array, Hash Table, Union Find]
294	Binary Tree Longest Consecutive Sequence.java	Medium	Java	[DFS, Divide and Conquer, Tree]
295	Number of Connected Components in an Undirected Graph.java	Medium	Java	[BFS, DFS, Graph, Union Find]
296	Next Closest Time.java	Medium	Java	[Basic Implementation, Enumeration, String]
297	Serialize and Deserialize Binary Tree.java	Hard	Java	[BFS, DFS, Deque, Design, Divide and Conquer, Tree]
298	Partition Array.java	Medium	Java	[Array, Quick Sort, Sort, Two Pointers]
299	Word Ladder.java	Medium	Java	[BFS]
300	Unique Word Abbreviation.java	Medium	Java	[Design, Hash Table]
301	Unique Binary Search Tree II.java	Medium	Java	[BST, DP, Divide and Conquer, Tree]
302	Ugly Number.java	Medium	Java	[Math]
303	Top K Frequent Words.java	Medium	Java	[Hash Table, Heap, MaxHeap, MinHeap, PriorityQueue, Trie]
304	Segment Tree Build.java	Medium	Java	[Binary Tree, Divide and Conquer, Lint, Segment Tree]
305	Segment Tree Build II.java	Medium	Java	[Binary Tree, Divide and Conquer, Lint, Segment Tree]
306	Segment Tree Query.java	Medium	Java	[Binary Tree, DFS, Divide and Conquer, Lint, Segment Tree]
307	Segment Tree Modify.java	Medium	Java	[Binary Tree, DFS, Divide and Conquer, Lint, Segment Tree]
308	Segment Tree Query II.java	Medium	Java	[Binary Tree, DFS, Divide and Conquer, Lint, Segment Tree]
309	Count of Smaller Numbers After Self.java	Hard	Java	[BST, Binary Indexed Tree, Binary Search, Divide and Conquer, Segment Tree]
310	ColorGrid.java	Medium	Java	[Design, Hash Table]
311	Container With Most Water.java	Medium	Java	[Array, Two Pointers]
312	Copy List with Random Pointer.java	Medium	Java	[Hash Table, Linked List]
313	Encode and Decode Strings.java	Medium	Java	[String]
314	Fast Power.java	Medium	Java	[DFS, Divide and Conquer]
315	Find the Connected Component in the Undirected Graph.java	Medium	Java	[BFS, DFS]
316	HashWithCustomizedClass(LinkedList).java	Medium	Java	[Hash Table]
317	Interval Minimum Number.java	Medium	Java	[Binary Search, Divide and Conquer, Lint, Segment Tree]
318	Interval Sum.java	Medium	Java	[Binary Search, Lint, Segment Tree]
319	Kth Smallest Element in a BST.java	Medium	Java	[BST, DFS, Stack, Tree]
320	Longest Common Prefix.java	Easy	Java	[String]
321	Majority Element II.java	Medium	Java	[Array]
322	Partition List.java	Medium	Java	[Linked List, Two Pointers]
323	Peeking Iterator.java	Medium	Java	[Design]
324	Rehashing.java	Medium	Java	[Hash Table]
325	Reorder List.java	Medium	Java	[Linked List]
326	Restore IP Addresses.java	Medium	Java	[Backtracking, DFS, String]
327	Reverse Words in a String.java	Medium	Java	[String]
328	Reverse Words in a String II.java	Medium	Java	[String]
329	Reverse Words in a String III.java	Easy	Java	[String]
330	Search a 2D Matrix.java	Medium	Java	[Array, Binary Search]
331	Search a 2D Matrix II.java	Medium	Java	[Binary Search, Divide and Conquer]
332	Search for a Range.java	Medium	Java	[Array, Binary Search]
333	Search Range in Binary Search Tree .java	Medium	Java	[BST, Binary Tree]
334	Merge Sorted Array II.java	Easy	Java	[Array]
335	Nth to Last Node in List.java	Easy	Java	[Linked List]
336	Sort List.java	Medium	Java	[Divide and Conquer, Linked List, Merge Sort, Sort]
337	Summary Ranges.java	Medium	Java	[Array]
338	Topological Sorting.java	Medium	Java	[BFS, DFS, Topological Sort]
339	Remove Duplicate Letters.java	Hard	Java	[Greedy, Hash Table, Stack]
340	Spiral Matrix.java	Medium	Java	[Array, Enumeration]
341	Expression Add Operators.java	Hard	Java	[Backtracking, DFS, Divide and Conquer, String]
342	Insert Interval.java	Hard	Java	[Array, PriorityQueue, Sort]
343	Shortest Palindrome.java	Hard	Java	[KMP, String]
344	Two Sum.java	Easy	Java	[Array, Hash Table]
345	K Empty Slots.java	Hard	Java	[Array, BST, TreeSet]
346	Count of Range Sum.java	Hard	Java	[BST, Divide and Conquer, Merge Sort, PreSum]
347	Max Sum of Rectangle No Larger Than K.java	Hard	Java	[Array, BST, Binary Search, DP, Queue, TreeSet]
348	Perfect Rectangle.java	Hard	Java	[Design, Geometry, Hash Table]
349	Construct Binary Tree from Inorder and Postorder Traversal.java	Medium	Java	[Array, DFS, Divide and Conquer, Tree]
350	Generate Parentheses.java	Medium	Java	[Backtracking, DFS, Sequence DFS, String]
351	Strobogrammatic Number II.java	Medium	Java	[DFS, Enumeration, Math, Sequence DFS]
352	Flip Game II.java	Medium	Java	[Backtracking, DFS, DP]
353	Max Area of Island.java	Easy	Java	[Array, DFS]
354	Max Points on a Line.java	Hard	Java	[Array, Geometry, Hash Table, Math]
355	Number of Digit One.java	Hard	Java	[Math]
356	Binary Representation.java	Hard	Java	[Bit Manipulation, String]
357	Palindrome Partitioning.java	Medium	Java	[Backtracking, DFS]
358	Recover Binary Search Tree.java	Hard	Java	[BST, DFS, Tree]
359	Subarray Sum.java	Easy	Java	[Array, Hash Table, PreSum, Subarray]
360	Submatrix Sum.java	Medium	Java	[Array, Hash Table, PreSum]
361	Longest Palindromic Substring.java	Medium	Java	[DP, String]
362	Longest Palindromic Subsequence.java	Medium	Java	[DFS, DP, Interval DP, Memoization]
363	Jump Game II.java	Hard	Java	[Array, Coordinate DP, DP, Greedy]
364	Gas Station.java	Medium	Java	[Greedy]
365	Triangles.java	Medium	Java	[Array, Coordinate DP, DFS, DP, Memoization]
366	Range Sum Query - Immutable.java	Easy	Java	[DP, PreSum]
367	Longest Valid Parentheses.java	Hard	Java	[Coordinate DP, Stack, String]
368	Remove Invalid Parentheses.java	Review	Java	[BFS, DFS, DP]
369	Merge Intervals.java	Medium	Java	[Array, PriorityQueue, Sort, Sweep Line]
370	H-Index.java	Medium	Java	[Bucket Sort, Hash Table, Sort]
371	H-Index II.java	Medium	Java	[Binary Search]
372	Sort Colors.java	Medium	Java	[Array, Partition, Quick Sort, Sort, Two Pointers]
373	Sort Colors II.java	Medium	Java	[Partition, Quick Sort, Sort, Two Pointers]
374	Sort Letters by Case.java	Medium	Java	[Partition, Sort, String, Two Pointers]
375	Subarray Sum Closest.java	Medium	Java	[PreSum, PriorityQueue, Sort, Subarray]
376	Task Scheduler.java	Medium	Java	[Array, Enumeration, Greedy, PriorityQueue, Queue]
377	Rearrange String k Distance Apart.java	Hard	Java	[Greedy, Hash Table, Heap]
378	Exam Room.java	Medium	Java	[PriorityQueue, Sort]
379	Anagrams.java	Medium	Java	[Array, Hash Table]
380	Path Sum IV.java	Medium	Java	[DFS, Hash Table, Tree]
381	Longest Words.java	Easy	Java	[Hash Table, String]
382	Unique Characters.java	Easy	Java	[Array, String]
383	Number Of Corner Rectangles.java	Medium	Java	[DP, Math]
384	Palindromic Substrings.java	Medium	Java	[DP, String]
385	Multiply Strings.java	Medium	Java	[Math, String]
386	Subsets.java	Medium	Java	[Array, BFS, Backtracking, Bit Manipulation, DFS]
387	Subsets II.java	Medium	Java	[Array, BFS, Backtracking, DFS]
388	Combination Sum.java	Medium	Java	[Array, Backtracking, Combination, DFS]
389	Combination Sum II.java	Medium	Java	[Array, Backtracking, Combination, DFS]
390	Combination Sum III.java	Medium	Java	[Array, Backtracking, Combination, DFS]
391	Product of Array Except Self.java	Medium	Java	[Array, PreProduct]
392	Total Hamming Distance.java	Medium	Java	[Bit Manipulation]
393	Smallest Subtree with all the Deepest Nodes.java	Medium	Java	[DFS, Divide and Conquer, Tree]
394	Binary Gap.java	Easy	Java	[Bit Manipulation]
395	Subarray Sum Equals K.java	Medium	Java	[Array, Hash Table, PreSum, Subarray]
396	Maximize Distance to Closest Person.java	Easy	Java	[Array]
397	Simplify Path.java	Medium	Java	[Stack, String]
398	Convert Binary Search Tree to Sorted Doubly Linked List (extra space).java	Medium	Java	[Linked List, Stack, Tree]
399	Paint Fence.java	Easy	Java	[DP, Sequence DP]
400	Binary Tree Zigzag Level Order Traversal.java	Medium	Java	[BFS, Stack, Tree]
401	Word Break.java	Medium	Java	[DP, Hash Table, Sequence DP]
402	Best Time to Buy and Sell Stock.java	Easy	Java	[Array, DP, Sequence DP]
403	Best Time to Buy and Sell Stock II.java	Easy	Java	[Array, DP, Greedy, Sequence DP, Status DP]
404	Longest Increasing Subsequence.java	Medium	Java	[Binary Search, Coordinate DP, DP, Memoization]
405	Best Time to Buy and Sell Stock with Transaction Fee.java	Medium	Java	[Array, DP, Greedy, Sequence DP, Status DP]
406	Random Pick Index.java	Medium	Java	[Reservior Sampling]
407	Find the Celebrity.java	Medium	Java	[Array, Greedy]
408	Sparse Matrix Multiplication.java	Medium	Java	[Hash Table]
409	Brick Wall.java	Medium	Java	[Hash Table]
410	Exclusive Time of Functions.java	Medium	Java	[Stack]
411	Friends Of Appropriate Ages.java	Medium	Java	[Array, Math]
412	Target Sum.java	Medium	Java	[DFS, DP]
413	Maximum Size Subarray Sum Equals k.java	Medium	Java	[Hash Table, PreSum, Subarray]
414	Contiguous Array.java	Medium	Java	[Hash Table]
415	Line Reflection.java	Medium	Java	[Hash Table, Math]
416	Insert Delete GetRandom O(1).java	Medium	Java	[Array, Design, Hash Table]
417	Number of Longest Increasing Subsequence.java	Medium	Java	[Coordinate DP, DP]
418	Minimum Swaps To Make Sequences Increasing.java	Medium	Java	[Coordinate DP, DP, Status DP]
419	Binary Tree Vertical Order Traversal.java	Medium	Java	[BFS, DFS, Hash Table, Tree]
420	Populating Next Right Pointers in Each Node II.java	Medium	Java	[DFS, Tree]
421	Search in Rotated Sorted Array.java	Medium	Java	[Array, Binary Search]
422	Minimum Subarray.java	Easy	Java	[Array, DP, Greedy, Sequence DP, Subarray]
423	Valid Number.java	Hard	Java	[Enumeration, Math, String]
424	Find the Weak Connected Component in the Directed Graph.java	Medium	Java	[Union Find]
425	Accounts Merge.java	Medium	Java	[DFS, Hash Table, Hash Table, Union Find]
426	Bricks Falling When Hit.java	Hard	Java	[Union Find]
427	Interval Sum II.java	Hard	Java	[Binary Search, Lint, Segment Tree]
428	Count of Smaller Number.java	Medium	Java	[Binary Search, Lint, Segment Tree]
429	HashHeap.java	Hard	Java	[HashHeap, Heap]
430	My Calendar I.java	Medium	Java	[Array, TreeMap]
431	Reverse Pairs.java	Medium	Java	[Binary Indexed Tree, Binary Search Tree, Divide and Conquer, Merge Sort, Segment Tree]
432	Trapping Rain Water II.java	Hard	Java	[BFS, Heap, MinHeap, PriorityQueue]
433	Kth Largest Element in an Array.java	Medium	Java	[Divide and Conquer, Heap, MinHeap, PriorityQueue, Quick Sort]
434	Merge k Sorted Lists.java	Medium	Java	[Divide and Conquer, Heap, Linked List, PriorityQueue]
435	Merge k Sorted Arrays.java	Medium	Java	[Heap, MinHeap, PriorityQueue]
436	Heapify.java	Medium	Java	[Heap, MinHeap]
437	Top K Frequent Elements.java	Medium	Java	[Hash Table, Heap, MaxHeap, MinHeap, PriorityQueue]
438	Ugly Number II.java	Medium	Java	[DP, Enumeration, Heap, Math, PriorityQueue]
439	Find Median from Data Stream.java	Hard	Java	[Design, Heap, MaxHeap, MinHeap]
440	Sliding Window Median.java	Hard	Java	[Design, Heap, MaxHeap, MinHeap, Sliding Window]
441	Inorder Successor in BST.java	Medium	Java	[BST, Tree]
442	Subtree of Another Tree.java	Easy	Java	[DFS, Divide and Conquer, Tree]
443	Two Sum IV - Input is a BST.java	Easy	Java	[Tree]
444	Read N Characters Given Read4.java	Easy	Java	[Enumeration, String]
445	Design Search Autocomplete System.java	Hard	Java	[Design, Hash Table, MinHeap, PriorityQueue, Trie]
446	Walls and Gates.java	Medium	Java	[BFS, DFS]
447	Merge Sorted Array.java	Easy	Java	[Array, Two Pointers]
448	Integer to English Words.java	Hard	Java	[Enumeration, Math, String]
449	Alien Dictionary.java	Hard	Java	[BFS, Backtracking, DFS, Graph, Topological Sort]
450	Valid Palindrome II.java	Easy	Java	[String]
451	Convert Binary Search Tree to Sorted Doubly Linked List.java	Medium	Java	[BST, DFS, Divide and Conquer, Linked List, Tree]
452	Word Ladder II.java	Hard	Java	[Array, BFS, Backtracking, DFS, Hash Table, String]
453	Moving Average from Data Stream.java	Easy	Java	[Design, Queue, Sliding Window]
454	Move Zeroes.java	Easy	Java	[Array, Two Pointers]
455	Flood Fill.java	Easy	Java	[DFS]
456	Diameter of Binary Tree.java	Easy	Java	[Tree]
457	Backspace String Compare.java	Easy	Java	[Stack, Two Pointers]
458	Text Justification.java	Hard	Java	[Enumeration, String]
459	Read N Characters Given Read4 II - Call multiple times.java	Hard	Java	[Enumeration, String]
460	Frog Jump.java	Hard	Java	[DP, Hash Table]
461	Longest Substring with At Most Two Distinct Characters.java	Hard	Java	[Hash Table, Sliding Window, String, Two Pointers]
462	Shortest Distance from All Buildings.java	Hard	Java	[BFS]
463	String to Integer (atoi).java	Medium	Java	[Math, String]
464	Roman to Integer.java	Easy	Java	[Math, String]
465	Intersection of Two Arrays.java	Easy	Java	[Binary Search, Hash Table, Sort, Two Pointers]
466	Strobogrammatic Number.java	Easy	Java	[Enumeration, Hash Table, Math]
467	Valid Parentheses.java	Easy	Java	[Stack, String]
468	First Unique Character in a String.java	Easy	Java	[Hash Table, String]
469	Add Binary.java	Easy	Java	[Math, String, Two Pointers]
470	Clone Graph.java	Medium	Java	[BFS, DFS, Graph]
471	Sliding Window Maximum.java	Hard	Java	[Deque, Heap, Sliding Window]
472	Median of Two Sorted Arrays.java	Hard	Java	[Array, Binary Search, DFS, Divide and Conquer]
473	Permutations.java	Medium	Java	[Backtracking, DFS, Permutation]
474	One Edit Distance.java	Medium	Java	[String]
475	4Sum.java	Medium	Java	[Hash Table]
476	Bus Routes.java	Hard	Java	[BFS]
477	Sliding Puzzle.java	Hard	Java	[BFS, Graph]
478	Isomorphic Strings.java	Easy	Java	[Hash Table]
479	Cracking the Safe.java	Hard	Java	[DFS, Greedy, Math]
480	Redundant Connection.java	Medium	Java	[BFS, DFS, Graph, Tree, Union Find]
481	Graph Valid Tree.java	Medium	Java	[BFS, DFS, Graph, Union Find]
482	Redundant Connection II.java	Hard	Java	[DFS, Graph, Tree, Union Find]
483	The Maze.java	Medium	Java	[BFS, DFS]
484	The Maze II.java	Medium	Java	[BFS, DFS, PriorityQueue]
485	The Maze III.java	Hard	Java	[BFS, DFS, PriorityQueue]
486	Predict the Winner.java	Medium	Java	[DP, MiniMax]
487	Next Greater Element I.java	Easy	Java	[Hash Table, Stack]
488	Group Shifted Strings.java	Medium	Java	[Hash Table, String]
489	Delete Digits.java	Medium	Java	[Greedy, Priority Queue]
490	Flatten 2D Vector.java	Medium	Java	[Design]
491	The Spiral Matrix II.java	Medium	Java	[Array]
492	Regular Expression Matching.java	Hard	Java	[Backtracking, DP, Double Sequence DP, Sequence DP, String]
493	Wildcard Matching.java	Hard	Java	[Backtracking, DP, Double Sequence DP, Greedy, Sequence DP, String]
494	Robot Room Cleaner.java	Hard	Java	[Backtracking, DFS]
495	Maximum Vacation Days.java	Hard	Java	[DP]