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