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