leetcode_Python

copyRight@Rajeev Ranjan

Links:

Websites
https://www.python.org/doc/ (Documentation Releases by Version)
https://www.python.org/downloads/ (Download the latest source release)
https://docs.python.org/3/tutorial/ (The Python Tutorial)
https://www.python.org/about/gettingstarted/ (Python For Beginners)
https://docs.python.org/3/library/ (The Python Standard Library)
https://wiki.python.org/moin/PythonPeriodicals (PythonPeriodicals)
https://packaging.python.org/ (Python Packaging User Guide)
https://pyvideo.org/ (Python related videos)
https://docs.python.org/3/ (Python 3.8.6rc1 documentation)

Notes:

Important
Python is an interpreted, high-level and general-purpose programming language. Created by Guido van Rossum and first released in 1991, Python's design philosophy emphasizes code readability with its notable use of significant whitespace.
Typing discipline: Duck, dynamic, gradual (since 3.5)
Designed by: Guido van Rossum
OS: Linux, macOS, Windows Vista (and newer) and more
Filename extensions: .py,.pyi,.pyc,.pyd,.pyo (prior to 3.5),.pyw,.pyz (since 3.5)

Table

#	Title	Solution	Difficulty	Tag
1	Two Sum	C++	Easy	Array / Hash Table
2	Add Two Numbers	C++	Medium	Linked List
3	Longest Substring Without Repeating Characters	C++	Medium	Hash Table / Two Pointers
4	Median of Two Sorted Arrays	C++	Hard	Array / Binary Search
5	Longest Palindromic Substring	C++	Medium	String
6	ZigZag Conversion	C++	Medium	String
7	Reverse Integer	C++	Easy	Math
8	String to Integer (atoi)	C++	Medium	String
9	Palindrome Number	C++	Easy	Math
10	Regular Expression Matching	C++	Hard	String / Dynamic Programming / Backtracking
11	Container With Most Water	C++	Medium	Array / Two Pointers
12	Integer to Roman	C++	Medium	String
13	Roman to Integer	C++	Easy	String
14	Longest Common Prefix	C++	Easy	String
15	3Sum	C++	Medium	Array / Two Pointers
16	3Sum Closest	C++	Medium	Array / Two Pointers
17	Letter Combinations of a Phone Number	C++	Medium	Backtracking / String
18	4Sum	C++	Medium	Array
19	Remove Nth Node From End of List	C++	Medium	Linked List / Two Pointers
20	Valid Parentheses	C++	Easy	Stack
21	Merge Two Sorted Lists	C++	Easy	Linked List
22	Generate Parentheses	C++	Medium	String / Backtracking
23	Merge k Sorted Lists	C++	Hard	Linked List / Heap
24	Swap Nodes in Pairs	C++	Medium	Linked List
25	Reverse Nodes in k-Group	C++	Hard	Linked List
26	Remove Duplicates from Sorted Array	C++	Easy	Array / Two Pointers
27	Remove Element	C++	Easy	Array / Two Pointers
28	Implement strStr()	C++	Easy	String
29	Implement strStr()	C++	Easy	String
31	Next Permutation	C++	Medium	Array
33	Search in Rotated Sorted Array	C++	Medium	Array / Binary Search
34	Search for a Range	C++	Medium	Array / Binary Search
35	Search Insert Position	C++	Easy	Array / Binary Search
36	Valid Sudoku	C++	Medium	Hash Table
37	Sudoku Solver	C++	Medium	Hash Table
38	Count and Say	C++	Easy	String
39	Combination Sum	C++	Medium	Array / Backtracking
40	Combination Sum II	C++	Medium	Array / Backtracking
41	First Missing Positive	C++	Hard	Array
42	Trapping Rain Water	C++	Hard	Array / Two Pointers / Stack
43	Multiply Strings	C++	Medium	String
44	Wildcard Matching	C++	Hard	String / Backtracking / Greedy
45	Jump Game II	C++	Hard	Array / Greedy
46	Permutations	C++	Medium	Backtracking
47	Permutations II	C++	Medium	Backtracking
48	Rotate Image	C++	Medium	Matrix
49	Group Anagrams	C++	Medium	Hash Table / String
50	Pow(x, n)	C++	Medium	Binary Search
51	Pow(x, n)	C++	Medium	Binary Search
52	Pow(x, n)	C++	Medium	Binary Search
53	Maximum Subarray	C++	Easy	Dynamic Programming / Array
54	Spiral Matrix	C++	Medium	Array
55	Jump Game	C++	Medium	Array / Greedy
56	Merge Intervals	C++	Medium	Array / Sort
57	Insert Interval	C++	Hard	Array / Sort
58	Length of Last Word	C++	Easy	String
59	Spiral Matrix II	C++	Medium	Array
60	Permutation Sequence	C++	Medium	Backtracking / Math
61	Rotate List	C++	Medium	Linked List / Two Pointers
62	Unique Paths	C++	Medium	Array / Dynamic Programming
63	Unique Paths II	C++	Medium	Array / Dynamic Programming
64	Minimum Path Sum	C++	Medium	Array / Dynamic Programming
65	Valid Number	C++	Medium	Array / Dynamic Programming
66	Plus One	C++	Easy	Array / Math
67	Add Binary	C++	Easy	String
68	Text Justification	C++	Hard	String
69	Sqrt(x)	C++	Easy	Binary Search / Math
70	Climbing Stairs	C++	Easy	Dynamic Programming
71	Simplify Path	C++	Medium	Stack / String
72	Edit Distance	C++	Medium	Stack / String
73	Set Matrix Zeroes	C++	Medium	Array
74	Search a 2D Matrix	C++	Medium	Array / Binary Search
75	Sort Colors	C++	Medium	Array / Two Pointers
76	Minimum Window Substring	C++	Hard	Hash Table / Two pointers / String
78	Subsets	C++	Medium	Array / Backtracking
79	Word Search	C++	Medium	Matrix / Backtracking
80	Remove Duplicates from Sorted Array II	C++	Medium	Array / Two Pointers
82	Remove Duplicates from Sorted List II	C++	Medium	Linked List
83	Remove Duplicates from Sorted List	C++	Easy	Linked List
84	Largest Rectangle in Histogram	C++	Hard	Array
85	Maximal Rectangle	C++	Hard	Array
86	Partition List	C++	Medium	Linked List
88	Merge Sorted Array	C++	Easy	Array / Two Pointers
90	Subsets II	C++	Medium	Array / Backtracking
91	Decode Ways	C++	Medium	Dynamic Programming / String
92	Reverse Linked List II	C++	Medium	Linked List
94	Binary Tree Inorder Traversal	C++	Medium	Tree / Stack
95	Unique Binary Search Trees II	C++	Medium	Tree
96	Unique Binary Search Trees	C++	Hard	Tree / DFS
97	Interleaving String	C++	Hard	Tree / DFS
98	Validate Binary Search Tree	C++	Medium	Tree
99	Recover Binary Search Tree	C++	Hard	Tree / DFS
100	Same Tree	C++	Easy	Tree / DFS
101	Symmetric Tree	C++	Easy	Tree
102	Binary Tree Level Order Traversal	C++	Medium	Tree / DFS / BFS
103	Binary Tree Zigzag Level Order Traversal	C++	Medium	Tree / BFS
104	Maximum Depth of Binary Tree	C++	Easy	Tree
105	Construct Binary Tree from Preorder and Inorder Traversal	C++	Medium	Array / Tree / DFS
106	Construct Binary Tree from Inorder and Postorder Traversal	C++	Medium	Linked List / DFS
107	Binary Tree Level Order Traversal II	C++	Easy	Tree
108	Convert Sorted Array to Binary Search Tree	C++	Easy	Tree / DFS
109	Convert Sorted List to Binary Search Tree	C++	Medium	Linked List / DFS
110	Balanced Binary Tree	C++	Easy	Tree / DFS
111	Minimum Depth of Binary Tree	C++	Easy	Tree
112	Path Sum	C++	Easy	Tree / DFS
113	Path Sum II	C++	Medium	Tree / DFS
114	Flatten Binary Tree to Linked List	C++	Medium	Tree / DFS
116	Populating Next Right Pointers in Each Node	C++	Medium	Tree / BFS
117	Populating Next Right Pointers in Each Node II	C++	Medium	Tree / Level-order Traversal
118	Pascal's Triangle	C++	Easy	Array
119	Pascal's Triangle II	C++	Easy	Array
120	Triangle	C++	Medium	Array / Dynamic Programming
121	Best Time to Buy and Sell Stock	C++	Easy	Array / Dynamic Programming
122	Best Time to Buy and Sell Stock	C++	Hard	Tree / DFS
123	Best Time to Buy and Sell Stock	C++	Hard	Tree / DFS
124	Binary Tree Maximum Path Sum	C++	Hard	Tree / DFS
125	Valid Palindrome	C++	Easy	String / Two Pointers
126	Word Ladder	C++	Hard	Array / Unoin Find
127	Word Ladder	C++	Medium	String / BFS
128	Longest Consecutive Sequence	C++	Hard	Array / Unoin Find
129	Sum Root to Leaf Numbers	C++	Medium	Tree / DFS / BFS
130	Surrounded Regions	C++	Medium	DFS / BFS / Union Find
131	Palindrome Partitioning	C++	Medium	Backtracking
132	Palindrome Partitioning	C++	Easy	Bit Manipulation
133	Clone Graph	C++	Medium	Graph / DFS / BFS
134	Gas Station	C++	Medium	Greedy
136	Single Number	C++	Easy	Bit Manipulation
137	Single Numberll	C++	Medium	Dynamic Programming
138	Copy List with Random Pointer	C++	Medium	Hash Table / Linked List
139	Word Break	C++	Medium	Dynamic Programming
140	Word BreakII	C++	Medium	Dynamic Programming
141	Linked List Cycle	C++	Easy	Linked List / Two Pointers
142	Linked List Cycle II	C++	Medium	Linked List / Two Pointers
143	Reorder List	C++	Medium	Linked List
144	Binary Tree Preorder Traversal	C++	Medium	Tree / Stack
145	Binary Tree Postorder Traversal	C++	Hard	Tree / Stack
146	LRU Cache	C++	Hard	Design
147	Insertion Sort List	C++	Easy	Stack / Design
148	Sort List	C++	Easy	Stack / Design
149	Max Points on a Line	C++	Easy	Stack / Design
151	Reverse Words in a String	C++	Medium	String
152	Maximum Product Subarray	C++	Hard	String / Two Pointers
153	Find Minimum in Rotated Sorted Array	C++	Hard	String / Two Pointers
154	Find Minimum in Rotated Sorted Array	C++	Hard	String / Two Pointers
155	Min Stack	C++	Easy	Stack / Design
157	Read N Characters Given Read4	C++	Easy	String
158	Read N Characters Given Read4 II - Call multiple times	C++	Hard	String
159	Longest Substring with At Most Two Distinct Characters	C++	Hard	String / Two Pointers
160	Intersection of Two Linked Lists	C++	Medium	String
161	One Edit Distance	C++	Medium	String
162	Find Peak Element	C++	Medium	Binary Search
163	Missing Ranges	C++	Medium	Array
168	Excel Sheet Column Title	C++	Easy	Math
169	Majority Element	C++	Easy	Array
171	Excel Sheet Column Number	C++	Easy	Math
173	Binary Search Tree Iterator	C++	Medium	Tree / Stack / Design
186	Reverse Words in a String II	C++	Medium	String
191	Number of 1 Bits	C++	Easy	Bit Manipulation
198	House Robber	C++	Easy	Dynamic Programming
200	Number of Islands	C++	Medium	BFS / Union Find
205	Isomorphic Strings	C++	Easy	Hash Table
206	Reverse Linked List	C++	Easy	Linked List
207	Course Schedule	C++	Medium	Graph / BFS / Topological Sort
208	Implement Trie (Prefix Tree)	C++	Medium	Trie / Design
209	Minimum Size Subarray Sum	C++	Medium	Array / Two Pointers
210	Course Schedule II	C++	Medium	Graph / BFS / Topological Sort
211	Add and Search Word - Data structure design	C++	Medium	Design / Trie
212	Word Search II	C++	Hard	Backtracking / Trie
214	Shortest Palindrome	C++	Hard	String
215	Kth Largest Element in an Array	C++	Medium	Sort / Partition
221	Maximal Square	C++	Medium	Dynamic Programming / BFS
223	Rectangle Area	C++	Medium	Math
224	Basic Calculator	C++	Hard	String / Stack
226	Invert Binary Tree	C++	Easy	Tree
227	Basic Calculator II	C++	Medium	String
228	Summary Ranges	C++	Medium	Array
229	Majority Element II	C++	Medium	Array
230	Kth Smallest Element in a BST	C++	Medium	Tree
231	Power of Two	C++	Easy	Bit Manipulation
234	Palindrome Linked List	C++	Easy	Linked List / Two Pointers
235	Lowest Common Ancestor of a Binary Search Tree	C++	Easy	Tree
236	Lowest Common Ancestor of a Binary Tree	C++	Medium	Tree
238	Product of Array Except Self	C++	Medium	Array
239	Sliding Window Maximum	C++	Hard	Heap
240	Search a 2D Matrix II	C++	Medium	Binary Search / Divide and Conquer
244	Shortest Word Distance II	C++	Medium	Hash Table / Design
246	Strobogrammatic Number	C++	Easy	Hash Table / Math
247	Strobogrammatic Number II	C++	Medium	Math / Recursion
249	Group Shifted Strings	C++	Medium	String
251	Flatten 2D Vector	C++	Medium	Design
252	Meeting Rooms	C++	Easy	Sort
253	Meeting Rooms II	C++	Medium	Heap / Sort
255	Verify Preorder Sequence in Binary Search Tree	C++	Medium	Stack / Tree
257	Binary Tree Paths	C++	Easy	Tree / DFS / BFS
258	Add Digits	C++	Easy	Math
259	3Sum Smaller	C++	Medium	Array / Two Pointers
261	Graph Valid Tree	C++	Medium	Graph / BFS / DFS / Union Find
263	Ugly Number	C++	Easy	Math
264	Ugly Number II	C++	Medium	Dynamic Programming / Math
266	Palindrome Permutation	C++	Easy	Hash Table
267	Palindrome Permutation II	C++	Medium	Backtracking
268	Missing Number	C++	Easy	Array / Bit Manipulation
269	Alien Dictionary	C++	Hard	Graph / Topological Sort
270	Closest Binary Search Tree Value	C++	Easy	Tree / Binary Search
271	Encode and Decode Strings	C++	Medium	String / Design
272	Closest Binary Search Tree Value II	C++	Hard	Tree / Stack
273	Integer to English Words	C++	Hard	String
274	H-Index	C++	Medium	Sort
275	H-Index II	C++	Medium	Binary Search
276	Paint Fence	C++	Easy	Dynamic Programming
277	Find the Celebrity	C++	Medium	Array
278	First Bad Version	C++	Easy	Binary Search
279	Perfect Squares	C++	Medium	Math / Dynamic Programming
280	Wiggle Sort	C++	Easy	Array
281	Zigzag Iterator	C++	Medium	Design
282	Expression Add Operators	C++	Hard	Divide and Conquer
283	Move Zeroes	C++	Easy	Array / Two Pointers
284	Peeking Iterator	C++	Medum	Design
285	Inorder Successor in BST	C++	Medium	Tree
286	Walls and Gates	C++	Medium	BFS
289	Game of Life	C++	Medium	Array
290	Word Pattern	C++	Easy	Hash Table
293	Flip Game	C++	Easy	String
294	Flip Game II	C++	Medium	Backtracking
295	Find Median from Data Stream	C++	Hard	Heap / Design
297	Serialize and Deserialize Binary Tree	C++	Hard	Tree / Design
298	Binary Tree Longest Consecutive Sequence	C++	Medium	Tree
300	Longest Increasing Subsequence	C++	Medium	Binary Search / Dynamic Programming
301	Remove Invalid Parentheses	C++	Hard	Backtracking / DFS / BFS
303	Range Sum Query - Immutable	C++	Easy	Dynamic Programming
304	Range Sum Query 2D - Immutable	C++	Medium	Dynamic Programming
305	Number of Islands II	C++	Hard	Union Find
307	Range Sum Query - Mutable	C++	Medium	Segment Tree
309	Best Time to Buy and Sell Stock with Cooldown	C++	Medium	Dynamic Programming
310	Minimum Height Trees	C++	Medium	BFS/ Graph
311	Sparse Matrix Multiplication	C++	Medium	Matrix
313	Super Ugly Number	C++	Medium	Dynamic Programming / Math
314	Binary Tree Vertical Order Traversal	C++	Medium	BFS
315	Count of Smaller Numbers After Self	C++	Hard	Divide and Conqur / Binary Search Tree
317	Shortest Distance from All Buildings	C++	Hard	BFS
318	Maximum Product of Word Lengths	C++	Medium	Bit Manipulation
323	Number of Connected Components in an Undirected Graph	C++	Medium	Graph / Union Find / BFS / DFS
325	Maximum Size Subarray Sum Equals k	C++	Medium	Array / Hash Table
329	Longest Increasing Path in a Matrix	C++	Hard	DFS / Memorization
331	Verify Preorder Serialization of a Binary Tree	C++	Medium	Stack
332	Reconstruct Itinerary	C++	Medium	Graph / DFS
333	Largest BST Subtree	C++	Medium	Tree
334	Increasing Triplet Subsequence	C++	Medium	Array
336	Palindrome Pairs	C++	Hard	Hash Table / String / Trie
339	Nested List Weight Sum	C++	Easy	DFS
340	Longest Substring with At Most K Distinct Characters	C++	Hard	Hash Table / String
341	Flatten Nested List Iterator	C++	Medium	Stack / Design
344	Reverse String	C++	Easy	String
347	Top K Frequent Elements	C++	Medium	Hash Table / Heap
348	Design Tic-Tac-Toe	C++	Medium	Design
351	Android Unlock Patterns	C++	Medium	DFS / Dynamic Programming
354	Russian Doll Envelopes	C++	Hard	Binary Search / Dynamic Programming
355	Design Twitter	C++	Medium	Hash Table / Design
359	Logger Rate Limiter	C++	Easy	Hash Table / Design
360	Sort Transformed Array	C++	Medium	Math / Two Pointers
361	Bomb Enemy	C++	Medium	Dynamic Programming
362	Design Hit Counter	C++	Medium	Design
364	Nested List Weight Sum II	C++	Medium	DFS
369	Plus One Linked List	C++	Medium	Linked List
373	Find K Pairs with Smallest Sums	C++	Medium	Heap
377	Combination Sum IV	C++	Medium	Dynamic Programming
378	Kth Smallest Element in a Sorted Matrix	C++	Medium	Binary Search / Heap
380	Insert Delete GetRandom O(1)	C++	Medium	Hash Table / Design
382	Linked List Random Node	C++	Medium	Reservoir Sampling
394	Decode String	C++	Medium	String / DFS
398	Random Pick Index	C++	Medium	Reservoir Sampling
399	Evaluate Division	C++	Medium	Graph
402	Remove K Digits	C++	Medium	Greedy
404	Sum of Left Leaves	C++	Easy	Tree
408	Valid Word Abbreviation	C++	Easy	String
409	Longest Palindrome	C++	Easy	Hash Table
411	Minimum Unique Word Abbreviation	C++	Hard	Backtracking
412	Fizz Buzz	C++	Easy	Array
416	Partition Equal Subset Sum	C++	Medium	Dynamic Programming
417	Pacific Atlantic Water Flow	C++	Medium	DFS / BFS
418	Sentence Screen Fitting	C++	Medium	Dynamic Programming
433	Minimum Genetic Mutation	C++	Medium	BFS
435	Non-overlapping Intervals	C++	Medium	Greedy
436	Find Right Interval	C++	Medium	Array / Binary Search
438	Find All Anagrams in a String	C++	Easy	Hash Table
441	Arranging Coins	C++	Easy	Math
444	Sequence Reconstruction	C++	Medium	Graph / Topological Sort
450	Delete Node in a BST	C++	Medium	Tree
451	Sort Characters By Frequency	C++	Medium	Hash Table / Heap
461	Hamming Distance	C++	Easy	Bit Manipulation
467	Unique Substrings in Wraparound String	C++	Medium	Dynamic Programming
473	Matchsticks to Square	C++	Medium	DFS
477	Total Hamming Distance	C++	Medium	Bit Manipulation
482	License Key Formatting	C++	Medium	Array
484	Find Permutation	C++	Medium	Greedy
486	Predict the Winner	C++	Medium	Dynamic Programming / Minimax
487	Max Consecutive Ones II	C++	Medium	Two Pointers
489	Robot Room Cleaner	C++	Hard	DFS
490	The Maze	C++	Medium	BFS / DFS
494	Target Sum	C++	Medium	Backtracking
496	Next Greater Element I	C++	Easy	Stack
498	Diagonal Traverse	C++	Medium	Matrix
499	The Maze III	C++	Hard	DFS / BFS
503	Next Greater Element II	C++	Medium	Stack
505	The Maze II	C++	Medium	DFS / BFS
508	Most Frequent Subtree Sum	C++	Medium	Tree / Hash Table
513	Find Bottom Left Tree Value	C++	Medium	Tree / BFS / DFS
515	Find Largest Value in Each Tree Row	C++	Medium	Tree / BFS / DFS
523	Continuous Subarray Sum	C++	Medium	Dynamic Programming
524	Longest Word in Dictionary through Deleting	C++	Medium	Two Pointers
525	Contiguous Array	C++	Medium	Hash Table
531	Lonely Pixel I	C++	Medium	Array / DFS
535	Encode and Decode TinyURL	C++	Medium	String
536	Construct Binary Tree from String	C++	Medium	String / Tree
538	Convert BST to Greater Tree	C++	Easy	DFS
540	Single Element in a Sorted Array	C++	Medium	Array / Binary Search
541	Reverse String II	C++	Easy	String
542	01 Matrix	C++	Medium	BFS / DFS
543	Diameter of Binary Tree	C++	Easy	Tree
547	Friend Circles	C++	Medium	DFS / Union Find
549	Binary Tree Longest Consecutive Sequence II	C++	Medium	Tree
554	Brick Wall	C++	Medium	Hash Table
556	Next Greater Element III	C++	Medium	String
560	Subarray Sum Equals K	C++	Medium	Array / Map
562	Longest Line of Consecutive One in Matrix	C++	Medium	Array
565	Array Nesting	C++	Medium	Array
566	Reshape the Matrix	C++	Easy	Array
567	Permutation in String	C++	Medium	Two Pointers
572	Subtree of Another Tree	C++	Easy	Tree
582	Kill Process	C++	Medium	Tree / BFS / DFS
583	Delete Operation for Two Strings	C++	Medium	Dynamic Programming
599	Minimum Index Sum of Two Lists	C++	Easy	Hash Table
606	Construct String from Binary Tree	C++	Easy	Tree / String
611	Valid Triangle Number	C++	Medium	Array
616	Add Bold Tag in String	C++	Medium	String
621	Task Scheduler	C++	Medium	Array / Queue
632	Smallest Range	C++	Hard	Two Pointers
633	Sum of Square Numbers	C++	Easy	Math
635	Design Log Storage System	C++	Medium	String / Design
636	Exclusive Time of Functions	C++	Medium	Stack
637	Average of Levels in Binary Tree	C++	Easy	BFS
639	Decode Ways II	C++	Hard	Dynamic Programming
642	Design Search Autocomplete System	C++	Hard	Design / Trie
643	Maximum Average Subarray I	C++	Easy	Array
645	Set Mismatch	C++	Easy	Hash Table / Math
647	Palindromic Substrings	C++	Medium	String
648	Replace Words	C++	Medium	Hash Table / Trie
652	Find Duplicate Subtrees	C++	Medium	Tree
653	Two Sum IV - Input is a BST	C++	Easy	DFS
654	Maximum Binary Tree	C++	Medium	Tree
657	Judge Route Circle	C++	Easy	String
658	Find K Closest Elements	C++	Medium	Binary Search
659	Split Array into Consecutive Subsequences	C++	Medium	Greedy
662	Maximum Width of Binary Tree	C++	Medium	Tree / BFS / DFS
663	Equal Tree Partition	C++	Medium	Tree
665	Non-decreasing Array	C++	Easy	Array
669	Trim a Binary Search Tree	C++	Easy	Tree
670	Maximum Swap	C++	Medium	Array / Math
671	Second Minimum Node In a Binary Tree	C++	Easy	Tree
673	Number of Longest Increasing Subsequence	C++	Medium	Dynamic Programming
674	Longest Continuous Increasing Subsequence	C++	Easy	Array
676	Implement Magic Dictionary	C++	Medium	Hash Table / Trie
677	Map Sum Pairs	C++	Medium	Trie
679	24 Game	C++	Hard	DFS
680	Valid Palindrome II	C++	Easy	String
681	Next Closest Time	C++	Medium	String
683	K Empty Slots	C++	Hard	Array / Binary Search
684	Redundant Connection	C++	Medium	Graph / Union Find
685	Redundant Connection II	C++	Hard	Graph / DFS / Union Find
686	Repeated String Match	C++	Easy	String
687	Longest Univalue Path	C++	Easy	Tree / DFS
688	Knight Probability in Chessboard	C++	Medium	Dynamic Programming
689	Maximum Sum of 3 Non-Overlapping Subarrays	C++	Hard	Array / Dynamic Programming
690	Employee Importance	C++	Easy	Hash Table / BFS / DFS
692	Top K Frequent Words	C++	Medium	Hash Table / Heap
693	Binary Number with Alternating Bits	C++	Easy	Bit Manipulation
694	Number of Distinct Islands	C++	Medium	Hash Table / DFS
695	Max Area of Island	C++	Easy	Array / DFS
696	Count Binary Substrings	C++	Easy	String
697	Degree of an Array	C++	Easy	Array
701	Insert into a Binary Search Tree	C++	Medium	Array
713	Subarray Product Less Than K	C++	Medium	Array
717	1-bit and 2-bit Characters	C++	Easy	Array
718	Maximum Length of Repeated Subarray	C++	Medium	Array / Dynamic Programming
720	Longest Word in Dictionary	C++	Easy	Hash Table / Trie
723	Candy Crush	C++	Medium	Array / Two Pointers
724	Find Pivot Index	C++	Easy	Array
725	Split Linked List in Parts	C++	Medium	Linked List
728	Self Dividing Numbers	C++	Easy	Math
729	My Calendar I	C++	Medium	Array
733	Flood Fill	C++	Easy	DFS
734	Sentence Similarity	C++	Easy	Hash Table
735	Asteroid Collision	C++	Medium	Stack
739	Daily Temperatures	C++	Medium	Stack / Hash Table
740	Delete and Earn	C++	Medium	Dynamic Programming
742	Closest Leaf in a Binary Tree	C++	Medium	Tree / Graph
746	Min Cost Climbing Stairs	C++	Easy	Array / Dynamic Programming
747	Largest Number At Least Twice of Others	C++	Easy	Array
750	Number Of Corner Rectangles	C++	Medium	Dynamic Programming
753	Cracking the Safe	C++	Hard	DFS
758	Bold Words in String	C++	Easy	String
760	Find Anagram Mappings	C++	Easy	Hash Table
763	Partition Labels	C++	Medium	Two Pointers / Greedy
765	Couples Holding Hands	C++	Hard	Greedy / Union Find / Greedy
766	Toeplitz Matrix	C++	Easy	Array
769	Max Chunks To Make Sorted	C++	Medium	Array
771	Jewels and Stones	C++	Easy	Hash Table
773	Sliding Puzzle	C++	Hard	BFS
777	Swap Adjacent in LR String	C++	Medium	Brainteaser
779	K-th Symbol in Grammar	C++	Medium	Recursion
783	Minimum Distance Between BST Nodes	C++	Easy	Tree
784	Letter Case Permutation	C++	Easy	String
785	Is Graph Bipartite	C++	Medium	Graph
787	Cheapest Flights Within K Stops	C++	Medium	Graph / Heap
791	Custom Sort String	C++	Medium	String
792	Number of Matching Subsequences	C++	Medium	Array
797	All Paths From Source to Target	C++	Medium	DFS / Graph
798	Smallest Rotation with Highest Score	C++	Hard	Array
799	Champagne Tower	C++	Medium	Array
802	Find Eventual Safe States	C++	Medium	DFS / Graph
803	Bricks Falling When Hit	C++	Hard	Union Find
804	Unique Morse Code Words	C++	Easy	String
805	Split Array With Same Average	C++	Hard	Math
806	Number of Lines To Write String	C++	Easy	String
807	Max Increase to Keep City Skyline	C++	Medium	Array
809	Expressive Words	C++	Medium	String
814	Binary Tree Pruning	C++	Medium	Tree
815	Bus Routes	C++	Hard	BFS
819	Most Common Word	C++	Easy	String
820	Short Encoding of Words	C++	Medium	Trie
821	Shortest Distance to a Character	C++	Easy	String
826	Most Profit Assigning Work	C++	Medium	Two Pointers / Binary Search
830	Positions of Large Groups	C++	Easy	Array
832	Flipping an Image	C++	Easy	Array
834	Sum of Distances in Tree	C++	Hard	Tree / DFS
836	Rectangle Overlap	C++	Easy	Math
841	Keys and Rooms	C++	Medium	DFS / BFS / Graph
843	Guess the Word	C++	Hard	Minimax
844	Backspace String Compare	C++	Easy	Stack / Two Pointers
845	Longest Mountain in Array	C++	Medium	Two Pointers
846	Hand of Straights	C++	Medium	Map
848	Shifting Letters	C++	Medium	String
849	Maximize Distance to Closest Person	C++	Easy	Array
852	Peak Index in a Mountain Array	C++	Easy	Binary Search
853	Car Fleet	C++	Medium	Stack
855	Exam Room	C++	Medium	Map
857	Minimum Cost to Hire K Workers	C++	Hard	Heap
859	Buddy Strings	C++	Easy	String
872	Leaf-Similar Trees	C++	Easy	Tree / DFS
876	Middle of the Linked List	C++	Easy	Linked List
884	Uncommon Words from Two Sentences	C++	Easy	Hash Table
888	Fair Candy Swap	C++	Easy	Array
889	Construct Binary Tree from Preorder and Postorder Traversal	C++	Medium	Tree
890	Find and Replace Pattern	C++	Medium	String
894	All Possible Full Binary Trees	C++	Medium	Tree / Recursion
896	Monotonic Array	C++	Easy	Array
900	RLE Iterator	C++	Medium	Array
904	Fruit Into Baskets	C++	Medium	Two Pointers
911	Online Election	C++	Medium	Binary Search / Map
914	X of a Kind in a Deck of Cards	C++	Easy	Array / Math
916	Word Subsets	C++	Medium	String
925	Long Pressed Name	C++	Easy	String
929	Unique Email Addresses	C++	Easy	String
932	Beautiful Array	C++	Medium	Divide and Conquer
933	Number of Recent Calls	C++	Easy	Queue
935	Knight Dialer	C++	Medium	Dynamic Programming
938	Range Sum of BST	C++	Medium	Tree
939	Minimum Area Rectangle	C++	Medium	Hash Table
941	Valid Mountain Array	C++	Easy	Array
946	Validate Stack Sequences	C++	Medium	Stack
951	Flip Equivalent Binary Trees	C++	Medium	Tree