leetcode

关于LeetCode 上的题目解析

LeetCode Algorithms

No.	Title	Solutions	Difficulty	Related Topics	Time Complexity	Space Complexity	Tag
867	Transpose Matrix	Java	Easy	Array	O(n)	O(1)
859	Buddy Strings	Java	Easy	String	O(n)
858	Mirror Reflection	Java	Medium	Math
852	Peak Index in a Mountain Array	Java	Easy	Binary Search
848	Shifting Letters	Java	Medium	String	O(n)	O(1)
846	Hand of Straights	Java Python	Medium	Map	O(nlogn)
844	Backspace String Compare	Java	Easy	Two Pointers Stack
832	Flipping an Image	Java	Easy	Array	O(n)	O(n)
819	Most Common Word	Java	Easy	String	O(n)		γ
812	Largest Triangle Area	Java	Easy	Math	O(n^3)		links
804	Unique Morse Code Words	Java Scala	Easy	String	O(n)	O(n)	≡
781	Rabbits in Forest	Java	Medium	HashTable Math	O(n)	O(1)
771	Jewels and Stones	Java	Easy	HashTable	O(n*m)
763	Partition Labels	Java	Medium	Two Pointer Greedy	O(n)	O(1)
713	Subarray Product Less Than K	Java	Medium	Array Two Poniter	O(n)	O(1)
704	Binary Search	Java	Easy	Binary Search	O(logn)	O(1)
696	Robot Return to Origin	Java	Easy	String	O(n)	O(1)	links
661	Image Smoother	Java	Easy	Array	O(n*m)	O(1)
657	Robot Return to Origin	Java	Easy	String
653	Two Sum IV - Input is a BST	Java	Easy	Tree	O(n)		γ
643	Maximum Average Subarray I	Java	Easy	Array	O(n)		γ
637	Average of Levels in Binary Tree	Java	Easy	Tree BFS
622	Design Circular Queue	Java	Medium	Design Queue	O(n)	O(1)	循环队列
599	Minimum Index Sum of Two Lists	Java	Easy	Hash Table	O(n)
561	Array Partition I	Java	Easy	Array
477	Total Hamming Distance	Java	Medium	Bit Manipulation	O(n)	O(1)	links
418	SentenceScreenFitting ♥		Easy				Locked
416	Partition Equal Subset Sum	Java	Medium
415	Add Strings	Java	Easy	Math	O(n)
414	Third Maximum Number	Java	Easy	Array	O(n)	O(1)
413	Arithmetic Slices	Java	Medium
412	Fizz Buzz	Java	Easy
410	Split Array Largest Sum	Java	Hard
409	Longest Palindrome	Java	Easy
406	Queue Reconstruction by Height	Java	Medium
405	Convert a Number to Hexadecimal	Java	Easy
404	Sum of Left Leaves	Java	Easy
403	Frog Jump	Java	Hard
402	Remove K Digits	Java	Medium
401	Binary Watch	Java	Easy
400	Nth Digit	Java	Easy
399	Evaluate Division	Java	Medium
398	Random Pick Index	Java	Medium
397	Integer Replacement	Java	Medium
396	Rotate Function	Java	Easy
395	Longest Substring with At Least K Repeating Characters	Java	Medium
394	Decode String	Java	Medium
393	UTF-8 Validation	Java	Medium
392	Is Subsequence	Java	Medium
391	Perfect Rectangle	Java	Hard
390	Elimination Game	Java	Medium
389	Find the Difference	Java	Easy
388	Longest Absolute File Path	Java	Medium
387	First Unique Character in a String	Java	Easy	Hash Table String	O(n)	O(1)
386	Lexicographical Numbers	Java	Medium
385	Mini Parser	Java	Medium
384	Shuffle an Array	Java	Medium
383	Ransom Note	Java	Easy
382	Linked List Random Node	Java	Medium
381	Insert Delete GetRandom O(1) - Duplicates allowed	Java	Hard
380	Insert Delete GetRandom O(1)	Java	Hard
377	Combination Sum IV	Java	Medium
376	Wiggle Subsequence	Java	Medium
371	Sum of Two Integers	Java	Easy
367	Valid Perfect Square	Java	Easy
350	Intersection of Two Arrays II	Java	Easy
349	Intersection of Two Arrays	Java	Easy
347	Top K Frequent Elements	Java	Medium
345	Reverse Vowels of a String	Java	Easy
344	Reverse String	Java	Easy
343	Integer Break	Java	Medium
342	Power of Four	Java	Easy
341	Flatten Nested List Iterator	Java	Medium
338	Counting Bits	Java	Medium
337	House Robber III	Java	Medium
336	Palindrome Pairs	Java	Hard
334	Increasing Triplet Subsequence	Java	Medium
332	Reconstruct Itinerary	Java	Medium
331	Verify Preorder Serialization of a Binary Tree	Java	Medium
330	Patching Array	Java	Medium
329	Longest Increasing Path in a Matrix	Java	Medium
328	Odd Even Linked List	Java	Easy
327	Count of Range Sum	Java	Hard
326	Power of Three	Java	Easy
324	Wiggle Sort II	Java	Medium
322	Coin Change	Java	Medium
321	Create Maximum Number	Java	Hard
319	Bulb Switcher	Java	Medium
318	Maximum Product of Word Lengths	Java	Medium
316	Remove Duplicate Letters	Java	Hard
315	Count of Smaller Numbers After Self	Java	Hard
313	Super Ugly Number	Java	Medium
312	Burst Balloons	Java	Hard
310	Minimum Height Trees	Java	Medium
307	Range Sum Query - Mutable	Java	Medium
306	Additive Number	Java	Medium
304	Range Sum Query 2D - Immutable	Java	Medium
303	Range Sum Query - Immutable	Java	Easy
301	Remove Invalid Parentheses	Java	Hard
300	Longest Increasing Subsequence	Java	Medium
299	Bulls and Cows	Java	Easy
297	Serialize and Deserialize Binary Tree	Java	Medium
295	Find Median from Data Stream	Java	Hard
292	Nim Game	Java	Easy
290	Word Pattern	Java	Easy
287	Find the Duplicate Number	Java	Hard
285	Inorder Successor in BST ♥		Medium				locked
284	Peeking Iterator	Java	Medium
283	Move Zeroes	Java	Easy
282	Expression Add Operators	Java	Hard
279	Perfect Squares	Java	Medium
278	First Bad Version	Java	Easy	Binary Search	O(logn)	O(1)	γ
275	H-Index II	Java	Medium
274	H-Index	Java	Medium
273	Integer to English Words	Java	Medium
268	Missing Number	Java	Medium
264	Ugly Number II	Java	Medium
263	Ugly Number	Java	Easy
260	Single Number III	Java	Medium
258	Add Digits	Java	Easy
257	Binary Tree Paths	Java	Easy
242	Valid Anagram	Java	Easy
241	Different Ways to Add Parentheses	Java	Medium
240	Search a 2D Matrix II	Java	Medium
239	Sliding Window Maximum	Java	Hard
238	Product of Array Except Self	Java	Medium
237	Delete Node in a Linked List	Java	Easy
236	Lowest Common Ancestor of a Binary Tree	Java, Scala	Medium
235	Lowest Common Ancestor of a Binary Search Tree	Java	Easy
234	Palindrome Linked List	Java	Easy
233	Number of Digit One	Java	Medium
232	Implement Queue using Stacks	Java	Easy	Stack Design	O(1)	O(1)
231	Power of Two	Java	Easy
230	Kth Smallest Element in a BST	Java	Medium
229	Majority Element II	Java	Medium
228	Summary Ranges	Java	Easy
227	Basic Calculator II	Java	Medium
226	Invert Binary Tree	Java	Easy
225	Implement Stack using Queues	Java	Medium
224	Basic Calculator	Java	Medium
223	Rectangle Area	Java	Easy
222	Count Complete Tree Nodes	Java	Medium
221	Maximal Square	Java	Medium
220	Contains Duplicate III	Java	Medium
219	Contains Duplicate II	Java	Easy
218	The Skyline Problem	Java	Hard
217	Contains Duplicate	Java	Easy
216	Combination Sum III	Java	Medium
215	Kth Largest Element in an Array	Java	Medium
214	Shortest Palindrome	Java	Hard
213	House Robber II	Java	Medium
212	Word Search II	Java	Hard
211	Add and Search Word - Data structure design	Java	Medium
210	Course Schedule II	Java	Medium
209	Minimum Size Subarray Sum	Java	Medium
208	Implement Trie (Prefix Tree)	Java	Medium
207	Course Schedule	Java	Medium
206	Reverse Linked List	Java, Java	Easy
205	Isomorphic Strings	Java	Easy
204	Count Primes	Java	Easy
203	Remove Linked List Elements	Java	Easy
202	Happy Number	Java	Easy
201	Bitwise AND of Numbers Range	Java	Medium
200	Number of Islands	Java	Medium
199	Binary Tree Right Side View	Java	Medium	O(nlogn)		Tree DFS BFS
198	House Robber	Java	Easy
195							shell
194							shell
193							shell
192							shell
191	Number of 1 Bits	Java	Easy
190	Reverse Bits	Java	Easy
189	Rotate Array	Java, Scala	Easy
188	Best Time to Buy and Sell Stock IV	Java	Hard
187	Repeated DNA Sequences	Java	Medium
186	Reverse Words in a String II ♥		Medium				locked
179	Largest Number	Java	Medium
174	Dungeon Game	Java	Hard
173	Binary Search Tree Iterator	Java, Scala	Medium
172	Factorial Trailing Zeroes	Java	Easy
171	Excel Sheet Column Number	Java	Easy
170	Two Sum III - Data structure design ♥	Java	Easy
169	Majority Element	Java	Easy
168	Excel Sheet Column Title	Java	Easy
167	Two Sum II - Input array is sorted ♥	Java	Easy	Two Pointer Array Binary Search	O(n)	O(1)
166	Fraction to Recurring Decimal	Java	Medium
165	Compare Version Numbers	Java	Easy
164	Maximum Gap	Java	Hard
163	Missing Ranges ♥	Java	Medium
162	Find Peak Element	Java	Medium
161	One Edit Distance♥	Java	Medium
160	Intersection of Two Linked Lists	Java	Easy
159	Longest Substring with At Most Two Distinct Characters ♥	Java	Hard
158	Read N Characters Given Read4 II - Call multiple times ♥	Java	Hard
157	Read N Characters Given Read4 ♥	Java	Easy
156	Binary Tree Upside Down ♥	Java	Medium
155	Min Stack	Java, Scala	Easy
154	Find Minimum in Rotated Sorted Array II	Java	Hard
153	Find Minimum in Rotated Sorted Array	Java, Java	Medium
152	Maximum Product Subarray	Java	Medium
151	Reverse Words in a String	Java, Java	Medium
150	Evaluate Reverse Polish Notation	Java	Medium
149	Max Points on a Line	Java	Hard
148	Sort List	Java	Medium
147	Insertion Sort List	Java	Medium
146	LRU Cache	Java, Scala	Hard
145	Binary Tree Postorder Traversal	Java	Hard
144	Binary Tree Preorder Traversal	Java, Java	Medium
143	Reorder List	Java	Medium
142	Linked List Cycle II	Java	Medium
141	Linked List Cycle	Java	Medium
140	Word Break II	Java	Hard
139	Word Break	Java	Medium
138	Copy List with Random Pointer	Java	Hard
137	Single Number II	Java	Medium
136	Single Number	Java	Medium
135	Candy	Java	Hard
134	Gas Station	Java	Medium
133	Clone Graph	Java	Medium
132	Palindrome Partitioning II	Java	Hard
131	Palindrome Partitioning	Java	Medium
130	Surrounded Regions	Java	Medium
129	Sum Root to Leaf Numbers	Java	Medium
128	Longest Consecutive Sequence	Java	Hard
127	Word Ladder	Java	Medium
126	Word Ladder II	Java	Hard
125	Valid Palindrome	Java, Scala	Easy
124	Binary Tree Maximum Path Sum	Java, Scala	Hard
123	Best Time to Buy and Sell Stock III	Java	Hard
122	Best Time to Buy and Sell Stock II	Java	Medium
121	Best Time to Buy and Sell Stock	Java	Medium
120	Triangle	Java, Java	Medium
119	Pascal’s Triangle II	Java	Easy
118	Pascal’s Triangle	Java	Easy
117	Populating Next Right Pointers in Each Node II	Java	Hard
116	Populating Next Right Pointers in Each Node	Java	Medium
115	Distinct Subsequences	Java	Hard
114	Flatten Binary Tree to Linked List	Java	Medium
113	Path Sum II	Java	Medium
112	Path Sum	Java	Easy
111	Minimum Depth of Binary Tree	Java	Easy
110	Balanced Binary Tree	Java, Java	Easy
109	Convert Sorted List to Binary Search Tree	Java	Medium
108	Convert Sorted Array to Binary Search Tree	Java	Medium
107	Binary Tree Level Order Traversal II	Java	Easy
106	Construct Binary Tree from Inorder and Postorder Traversal	Java	Medium
105	Construct Binary Tree from Preorder and Inorder Traversal	Java	Medium
104	Maximum Depth of Binary Tree	Java, Scala	Easy
103	Binary Tree Zigzag Level Order Traversal	Java	Medium
102	Binary Tree Level Order Traversal	Java, Scala	Easy
101	Symmetric Tree	Java	Easy	Tree Breadth-first Search Depth-first Search	O(nlogn)
100	Same Tree	Java	Easy	Tree Depth-first Search	O(nlogn)
99	Recover Binary Search Tree	Java	Hard
98	Validate Binary Search Tree	Java, Scala	Medium
97	Interleaving String	Java	Hard
96	Unique Binary Search Trees	Java	Medium
95	Unique Binary Search Trees II	Java	Medium
94	Binary Tree Inorder Traversal	Java	Medium
93	Restore IP Addresses	Java	Medium
92	Reverse Linked List II	Java, Scala	Medium
91	Decode Ways	Java	Medium
90	Subsets II	Java	Medium
89	Gray Code	Java	Medium
88	Merge Sorted Array	Java	Easy
87	Scramble String	Java	Hard
86	Partition List	Java	Medium
85	Maximal Rectangle	Java	Hard
84	Largest Rectangle in Histogram	Java	Hard
83	Remove Duplicates from Sorted List	Java	Easy
82	Remove Duplicates from Sorted List II	Java	Medium
81	Search in Rotated Sorted Array II	Java	Medium
80	Remove Duplicates from Sorted Array II	Java	Medium
79	Word Search	Java	Medium
78	Subsets	Java, Scala	Medium
77	Combinations	Java	Medium
76	Minimum Window Substring	Java	Hard
75	Sort Colors	Java	Medium
74	Search a 2D Matrix	Java, Scala	Medium
73	Set Matrix Zeroes	Java	Medium
72	Edit Distance	Java	Hard
71	Simplify Path	Java	Medium
70	Climbing Stairs	Java	Easy
69	Sqrt(x)	Java	Medium
68	Text Justification	Java	Hard
67	Add Binary	Java	Easy
66	Plus One	Java	Easy	Array Math	O(n)	O(1)
65	Valid Number	Java	Easy
64	Minimum Path Sum	Java	Medium	Array Dynamic Programming	O(M*N)	O(1)
63	Unique Paths II	Java	Medium	Array Dynamic Programming	O(w*h)	O(1)
62	Unique Paths	Java, Scala	Medium
61	Rotate List	Java	Medium
60	Permutation Sequence	Java	Medium
59	Spiral Matrix II	Java	Medium	Array	O(n^2)	O(1)
58	Length of Last Word	Java	Easy
57	Insert Interval	Java	Hard
56	Merge Intervals	Java	Hard
55	Jump Game	Java	Medium	Array Greedy	O(n)	O(1)	Q45
54	Spiral Matrix	Java	Medium
53	Maximum Subarray	Java	Medium	Array Dynamic Programming Divide and Conquer	O(n)
52	N-Queens II	Java	Hard
51	N-Queens	Java	Hard
50	“Pow(x, n)”	Java	Medium
49	Group Anagrams	Java	Medium
48	Rotate Image	Java	Medium
47	Permutations II	Java	Hard
46	Permutations	Java	Medium
45	Jump Game II	Java	Hard	Array Greedy	O(n)	O(1)	Q55
44	Wildcard Matching	Java	Hard
43	Multiply Strings	Java	Medium
42	Trapping Rain Water	Java	Hard
41	First Missing Positive	Java	Hard	Array	O(n)	O(1)	分桶
40	Combination Sum II	Java	Medium
39	Combination Sum	Java	Medium
38	Count and Say	Java	Easy
37	Sudoku Solver	Java	Hard
36	Valid Sudoku	Java	Easy
35	Search Insert Position	Java	Easy	Array Binary Search	O(N)
34	Find First and Last Position of Element in Sorted Array	Java	Medium	Array Binary Search	O(n)	O(1)
33	Search in Rotated Sorted Array	Java	Medium	Array Binary Search	O(logn)	O(1)	二分查找法
32	Longest Valid Parentheses	Java	Hard	String Dynamic Programming
31	Next Permutation	Java	Medium
30	Substring with Concatenation of All Words	Java	Hard	String Hash Table Two Pointer	O(M*N)
29	Divide Two Integers	Java	Medium
28	Implement strStr()	Java, Scala	Easy
27	Remove Element	Java	Easy
26	Remove Duplicates from Sorted Array	Java	Easy	Array Two Pointer	O(n)	O(1)
25	Reverse Nodes in k-Group	Java	Hard
24	Swap Nodes in Pairs	Java	Medium
23	Merge k Sorted Lists	Java	Hard
22	Generate Parentheses	Java	Medium
21	Merge Two Sorted Lists	Java	Easy
20	Valid Parentheses	Java	Easy	String Stack	O(n)
19	Remove Nth Node From End of List	Java	Medium	Linked List Two Pointer	O(N)		γ
18	4Sum	Java	Medium	Array HashTable TwoPointer	O(N^4)		Q15
17	Letter Combinations of a Phone Number	Java	Medium	String BackTracking	O(n^3)		queue
16	3Sum Closest	Java	Medium	Array Two Point	O(n^2)		Q15
15	3Sum	Java	Medium	Array Two Point	O(n^2)		good γ
14	Longest Common Prefix	Java	Easy	String	O(M*N)
13	Roman to Integer	Java	Easy	Math String			Q12
12	Integer to Roman	Java	Medium	Math String			Q13
11	Container With Most Water	Java	Medium
10	Regular Expression Matching	Java	Hard	String Dynamic Programming Backtracking
9	Palindrome Number	Java	Easy	Math	O(n)	O(1)	回文
8	String to Integer (atoi)	Java	Medium	Math String
7	Reverse Integer	Java Scala	Easy	Math
6	ZigZag Conversion	Java	Medium	String
5	Longest Palindromic Substring	Java	Medium	String Dynamic Programming
4	Median of Two Sorted Arrays	Java	Hard
3	Longest Substring Without Repeating Characters	Java	Medium
2	Add Two Numbers	Java	Medium
1	Two Sum	Python Java Scala	Easy	Array HashTable

LeetCode Shell

#	Title	Solution	Difficulty
195	Tenth Line		Easy
194	Transpose File		Medium
193	Valid Phone Numbers		Easy
192	Word Frequency		Medium

LeetCode Database

| # | Title | Solution | Difficulty | |—| —– | ——– | ———- | | | | | |

其他

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