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LeetCode

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Solutions

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#	Solution	Tags	Difficulty
1	Two Sum	Array,Hash Table	Easy
2	Add Two Numbers	Linked List,Math	Medium
3	Longest Substring Without Repeating Characters	Hash Table,Two Pointers,String,Sliding Window	Medium
4	Median of Two Sorted Arrays	Array,Binary Search,Divide and Conquer	Hard
5	Longest Palindromic Substring	String,Dynamic Programming	Medium
6	ZigZag Conversion	String	Medium
7	Reverse Integer	Math	Easy
8	String to Integer (atoi)	Math,String	Medium
9	Palindrome Number	Math	Easy
10	Regular Expression Matching	String,Dynamic Programming,Backtracking	Hard
11	Container With Most Water	Array,Two Pointers	Medium
12	Integer to Roman	Math,String	Medium
13	Roman to Integer	Math,String	Easy
14	Longest Common Prefix	String	Easy
15	3Sum	Array,Two Pointers	Medium
16	3Sum Closest	Array,Two Pointers	Medium
17	Letter Combinations of a Phone Number	String,Backtracking	Medium
18	4Sum	Array,Hash Table,Two Pointers	Medium
19	Remove Nth Node From End of List	Linked List,Two Pointers	Medium
20	Valid Parentheses	Stack,String	Easy
21	Merge Two Sorted Lists	Linked List	Easy
22	Generate Parentheses	String,Backtracking	Medium
23	Merge k Sorted Lists	Heap,Linked List,Divide and Conquer	Hard
24	Swap Nodes in Pairs	Linked List	Medium
25	Reverse Nodes in k-Group	Linked List	Hard
26	Remove Duplicates from Sorted Array	Array,Two Pointers	Easy
27	Remove Element	Array,Two Pointers	Easy
28	Implement strStr()	Two Pointers,String	Easy
29	Divide Two Integers	Math,Binary Search	Medium
30	Substring with Concatenation of All Words	Hash Table,Two Pointers,String	Hard
31	Next Permutation	Array	Medium
32	Longest Valid Parentheses	String,Dynamic Programming	Hard
33	Search in Rotated Sorted Array	Array,Binary Search	Medium
34	Find First and Last Position of Element in Sorted Array	Array,Binary Search	Medium
35	Search Insert Position	Array,Binary Search	Easy
36	Valid Sudoku	Hash Table	Medium
37	Sudoku Solver	Hash Table,Backtracking	Hard
38	Count and Say	String	Easy
39	Combination Sum	Array,Backtracking	Medium
40	Combination Sum II	Array,Backtracking	Medium
41	First Missing Positive	Array	Hard
42	Trapping Rain Water	Stack,Array,Two Pointers	Hard
43	Multiply Strings	Math,String	Medium
44	Wildcard Matching	Greedy,String,Dynamic Programming,Backtracking	Hard
45	Jump Game II	Greedy,Array	Hard
46	Permutations	Backtracking	Medium
47	Permutations II	Backtracking	Medium
48	Rotate Image	Array	Medium
49	Group Anagrams	Hash Table,String	Medium
50	Pow(x, n)	Math,Binary Search	Medium
51	N-Queens	Backtracking	Hard
52	N-Queens II	Backtracking	Hard
53	Maximum Subarray	Array,Divide and Conquer,Dynamic Programming	Easy
54	Spiral Matrix	Array	Medium
55	Jump Game	Greedy,Array	Medium
56	Merge Intervals	Sort,Array	Medium
57	Insert Interval	Sort,Array	Hard
58	Length of Last Word	String	Easy
59	Spiral Matrix II	Array	Medium
60	Permutation Sequence	Math,Backtracking	Medium
61	Rotate List	Linked List,Two Pointers	Medium
62	Unique Paths	Array,Dynamic Programming	Medium
63	Unique Paths II	Array,Dynamic Programming	Medium
64	Minimum Path Sum	Array,Dynamic Programming	Medium
65	Valid Number	Math,String	Hard
66	Plus One	Array	Easy
67	Add Binary	Math,String	Easy
68	Text Justification	String	Hard
69	Sqrt(x)	Math,Binary Search	Easy
70	Climbing Stairs	Dynamic Programming	Easy
71	Simplify Path	Stack,String	Medium
72	Edit Distance	String,Dynamic Programming	Hard
73	Set Matrix Zeroes	Array	Medium
74	Search a 2D Matrix	Array,Binary Search	Medium
75	Sort Colors	Sort,Array,Two Pointers	Medium
76	Minimum Window Substring	Hash Table,Two Pointers,String,Sliding Window	Hard
77	Combinations	Backtracking	Medium
78	Subsets	Bit Manipulation,Array,Backtracking	Medium
79	Word Search	Array,Backtracking	Medium
80	Remove Duplicates from Sorted Array II	Array,Two Pointers	Medium
81	Search in Rotated Sorted Array II	Array,Binary Search	Medium
82	Remove Duplicates from Sorted List II	Linked List	Medium
83	Remove Duplicates from Sorted List	Linked List	Easy
84	Largest Rectangle in Histogram	Stack,Array	Hard
85	Maximal Rectangle	Stack,Array,Hash Table,Dynamic Programming	Hard
86	Partition List	Linked List,Two Pointers	Medium
87	Scramble String	String,Dynamic Programming	Hard
88	Merge Sorted Array	Array,Two Pointers	Easy
89	Gray Code	Backtracking	Medium
90	Subsets II	Array,Backtracking	Medium
91	Decode Ways	String,Dynamic Programming	Medium
92	Reverse Linked List II	Linked List	Medium
93	Restore IP Addresses	String,Backtracking	Medium
94	Binary Tree Inorder Traversal	Stack,Tree,Hash Table	Medium
95	Unique Binary Search Trees II	Tree,Dynamic Programming	Medium
96	Unique Binary Search Trees	Tree,Dynamic Programming	Medium
97	Interleaving String	String,Dynamic Programming	Hard
98	Validate Binary Search Tree	Tree,Depth-first Search	Medium
99	Recover Binary Search Tree	Tree,Depth-first Search	Hard
100	Same Tree	Tree,Depth-first Search	Easy
101	Symmetric Tree	Tree,Depth-first Search,Breadth-first Search	Easy
102	Binary Tree Level Order Traversal	Tree,Breadth-first Search	Medium
103	Binary Tree Zigzag Level Order Traversal	Stack,Tree,Breadth-first Search	Medium
104	Maximum Depth of Binary Tree	Tree,Depth-first Search	Easy
105	Construct Binary Tree from Preorder and Inorder Traversal	Tree,Depth-first Search,Array	Medium
106	Construct Binary Tree from Inorder and Postorder Traversal	Tree,Depth-first Search,Array	Medium
107	Binary Tree Level Order Traversal II	Tree,Breadth-first Search	Easy
108	Convert Sorted Array to Binary Search Tree	Tree,Depth-first Search	Easy
109	Convert Sorted List to Binary Search Tree	Depth-first Search,Linked List	Medium
110	Balanced Binary Tree	Tree,Depth-first Search	Easy
111	Minimum Depth of Binary Tree	Tree,Depth-first Search,Breadth-first Search	Easy
112	Path Sum	Tree,Depth-first Search	Easy
113	Path Sum II	Tree,Depth-first Search	Medium
114	Flatten Binary Tree to Linked List	Tree,Depth-first Search	Medium
115	Distinct Subsequences	String,Dynamic Programming	Hard
116	Populating Next Right Pointers in Each Node	Tree,Depth-first Search	Medium
117	Populating Next Right Pointers in Each Node II	Tree,Depth-first Search	Medium
118	Pascal's Triangle	Array	Easy
119	Pascal's Triangle II	Array	Easy
120	Triangle	Array,Dynamic Programming	Medium
121	Best Time to Buy and Sell Stock	Array,Dynamic Programming	Easy
122	Best Time to Buy and Sell Stock II	Greedy,Array	Easy
123	Best Time to Buy and Sell Stock III	Array,Dynamic Programming	Hard
124	Binary Tree Maximum Path Sum	Tree,Depth-first Search	Hard
125	Valid Palindrome	Two Pointers,String	Easy
126	Word Ladder II	Breadth-first Search,Array,String,Backtracking	Hard
127	Word Ladder	Breadth-first Search	Medium
128	Longest Consecutive Sequence	Union Find,Array	Hard
129	Sum Root to Leaf Numbers	Tree,Depth-first Search	Medium
130	Surrounded Regions	Depth-first Search,Breadth-first Search,Union Find	Medium
131	Palindrome Partitioning	Backtracking	Medium
132	Palindrome Partitioning II	Dynamic Programming	Hard
133	Clone Graph	Depth-first Search,Breadth-first Search,Graph	Medium
134	Gas Station	Greedy	Medium
135	Candy	Greedy	Hard
136	Single Number	Bit Manipulation,Hash Table	Easy
137	Single Number II	Bit Manipulation	Medium
138	Copy List with Random Pointer	Hash Table,Linked List	Medium
139	Word Break	Dynamic Programming	Medium
140	Word Break II	Dynamic Programming,Backtracking	Hard
141	Linked List Cycle	Linked List,Two Pointers	Easy
142	Linked List Cycle II	Linked List,Two Pointers	Medium
143	Reorder List	Linked List	Medium
144	Binary Tree Preorder Traversal	Stack,Tree	Medium
145	Binary Tree Postorder Traversal	Stack,Tree	Hard
146	LRU Cache	Design	Medium
147	Insertion Sort List	Sort,Linked List	Medium
148	Sort List	Sort,Linked List	Medium
149	Max Points on a Line	Hash Table,Math	Hard
150	Evaluate Reverse Polish Notation	Stack	Medium
151	Reverse Words in a String	String	Medium
152	Maximum Product Subarray	Array,Dynamic Programming	Medium
153	Find Minimum in Rotated Sorted Array	Array,Binary Search	Medium
154	Find Minimum in Rotated Sorted Array II	Array,Binary Search	Hard
155	Min Stack	Stack,Design	Easy
156	Binary Tree Upside Down	Tree	Medium
157	Read N Characters Given Read4	String	Easy
158	Read N Characters Given Read4 II - Call multiple times	String	Hard
159	Longest Substring with At Most Two Distinct Characters	Hash Table,Two Pointers,String,Sliding Window	Medium
160	Intersection of Two Linked Lists	Linked List	Easy
161	One Edit Distance	String	Medium
162	Find Peak Element	Array,Binary Search	Medium
163	Missing Ranges	Array	Medium
164	Maximum Gap	Sort	Hard
165	Compare Version Numbers	String	Medium
166	Fraction to Recurring Decimal	Hash Table,Math	Medium
167	Two Sum II - Input array is sorted	Array,Two Pointers,Binary Search	Easy
168	Excel Sheet Column Title	Math	Easy
169	Majority Element	Bit Manipulation,Array,Divide and Conquer	Easy
170	Two Sum III - Data structure design	Design,Hash Table	Easy
171	Excel Sheet Column Number	Math	Easy
172	Factorial Trailing Zeroes	Math	Easy
173	Binary Search Tree Iterator	Stack,Tree,Design	Medium
174	Dungeon Game	Binary Search,Dynamic Programming	Hard
175	Combine Two Tables		Easy
176	Second Highest Salary		Easy
177	Nth Highest Salary		Medium
178	Rank Scores		Medium
179	Largest Number	Sort	Medium
180	Consecutive Numbers		Medium
181	Employees Earning More Than Their Managers		Easy
182	Duplicate Emails		Easy
183	Customers Who Never Order		Easy
184	Department Highest Salary		Medium
185	Department Top Three Salaries		Hard
186	Reverse Words in a String II	String	Medium
187	Repeated DNA Sequences	Bit Manipulation,Hash Table	Medium
188	Best Time to Buy and Sell Stock IV	Dynamic Programming	Hard
189	Rotate Array	Array	Easy
190	Reverse Bits	Bit Manipulation	Easy
191	Number of 1 Bits	Bit Manipulation	Easy
192	Word Frequency		Medium
193	Valid Phone Numbers		Easy
194	Transpose File		Medium
195	Tenth Line		Easy
196	Delete Duplicate Emails		Easy
197	Rising Temperature		Easy
198	House Robber	Dynamic Programming	Easy
199	Binary Tree Right Side View	Tree,Depth-first Search,Breadth-first Search	Medium
200	Number of Islands	Depth-first Search,Breadth-first Search,Union Find	Medium
201	Bitwise AND of Numbers Range	Bit Manipulation	Medium
202	Happy Number	Hash Table,Math	Easy
203	Remove Linked List Elements	Linked List	Easy
204	Count Primes	Hash Table,Math	Easy
205	Isomorphic Strings	Hash Table	Easy
206	Reverse Linked List	Linked List	Easy
207	Course Schedule	Depth-first Search,Breadth-first Search,Graph,Topological Sort	Medium
208	Implement Trie (Prefix Tree)	Design,Trie	Medium
209	Minimum Size Subarray Sum	Array,Two Pointers,Binary Search	Medium
210	Course Schedule II	Depth-first Search,Breadth-first Search,Graph,Topological Sort	Medium
211	Add and Search Word - Data structure design	Design,Trie,Backtracking	Medium
212	Word Search II	Trie,Backtracking	Hard
213	House Robber II	Dynamic Programming	Medium
214	Shortest Palindrome	String	Hard
215	Kth Largest Element in an Array	Heap,Divide and Conquer	Medium
216	Combination Sum III	Array,Backtracking	Medium
217	Contains Duplicate	Array,Hash Table	Easy
218	The Skyline Problem	Heap,Binary Indexed Tree,Segment Tree,Divide and Conquer,Line Sweep	Hard
219	Contains Duplicate II	Array,Hash Table	Easy
220	Contains Duplicate III	Sort,Ordered Map	Medium
221	Maximal Square	Dynamic Programming	Medium
222	Count Complete Tree Nodes	Tree,Binary Search	Medium
223	Rectangle Area	Math	Medium
224	Basic Calculator	Stack,Math	Hard
225	Implement Stack using Queues	Stack,Design	Easy
226	Invert Binary Tree	Tree	Easy
227	Basic Calculator II	String	Medium
228	Summary Ranges	Array	Medium
229	Majority Element II	Array	Medium
230	Kth Smallest Element in a BST	Tree,Binary Search	Medium
231	Power of Two	Bit Manipulation,Math	Easy
232	Implement Queue using Stacks	Stack,Design	Easy
233	Number of Digit One	Math	Hard
234	Palindrome Linked List	Linked List,Two Pointers	Easy
235	Lowest Common Ancestor of a Binary Search Tree	Tree	Easy
236	Lowest Common Ancestor of a Binary Tree	Tree	Medium
237	Delete Node in a Linked List	Linked List	Easy
238	Product of Array Except Self	Array	Medium
239	Sliding Window Maximum	Heap,Sliding Window	Hard
240	Search a 2D Matrix II	Binary Search,Divide and Conquer	Medium
241	Different Ways to Add Parentheses	Divide and Conquer	Medium
242	Valid Anagram	Sort,Hash Table	Easy
243	Shortest Word Distance	Array	Easy
244	Shortest Word Distance II	Design,Hash Table	Medium
245	Shortest Word Distance III	Array	Medium
246	Strobogrammatic Number	Hash Table,Math	Easy
247	Strobogrammatic Number II	Recursion,Math	Medium
248	Strobogrammatic Number III	Recursion,Math	Hard
249	Group Shifted Strings	Hash Table,String	Medium
250	Count Univalue Subtrees	Tree	Medium
251	Flatten 2D Vector	Design	Medium
252	Meeting Rooms	Sort	Easy
253	Meeting Rooms II	Heap,Greedy,Sort	Medium
254	Factor Combinations	Backtracking	Medium
255	Verify Preorder Sequence in Binary Search Tree	Stack,Tree	Medium
256	Paint House	Dynamic Programming	Easy
257	Binary Tree Paths	Tree,Depth-first Search	Easy
258	Add Digits	Math	Easy
259	3Sum Smaller	Array,Two Pointers	Medium
260	Single Number III	Bit Manipulation	Medium
261	Graph Valid Tree	Depth-first Search,Breadth-first Search,Union Find,Graph	Medium
262	Trips and Users		Hard
263	Ugly Number	Math	Easy
264	Ugly Number II	Heap,Math,Dynamic Programming	Medium
265	Paint House II	Dynamic Programming	Hard
266	Palindrome Permutation	Hash Table	Easy
267	Palindrome Permutation II	Backtracking	Medium
268	Missing Number	Bit Manipulation,Array,Math	Easy
269	Alien Dictionary	Graph,Topological Sort	Hard
270	Closest Binary Search Tree Value	Tree,Binary Search	Easy
271	Encode and Decode Strings	String	Medium
272	Closest Binary Search Tree Value II	Stack,Tree	Hard
273	Integer to English Words	Math,String	Hard
274	H-Index	Sort,Hash Table	Medium
275	H-Index II	Binary Search	Medium
276	Paint Fence	Dynamic Programming	Easy
277	Find the Celebrity	Array	Medium
278	First Bad Version	Binary Search	Easy
279	Perfect Squares	Breadth-first Search,Math,Dynamic Programming	Medium
280	Wiggle Sort	Sort,Array	Medium
281	Zigzag Iterator	Design	Medium
282	Expression Add Operators	Divide and Conquer	Hard
283	Move Zeroes	Array,Two Pointers	Easy
284	Peeking Iterator	Design	Medium
285	Inorder Successor in BST	Tree	Medium
286	Walls and Gates	Breadth-first Search	Medium
287	Find the Duplicate Number	Array,Two Pointers,Binary Search	Medium
288	Unique Word Abbreviation	Design,Hash Table	Medium
289	Game of Life	Array	Medium
290	Word Pattern	Hash Table	Easy
291	Word Pattern II	Backtracking	Hard
292	Nim Game	Brainteaser,Minimax	Easy
293	Flip Game	String	Easy
294	Flip Game II	Minimax,Backtracking	Medium
295	Find Median from Data Stream	Heap,Design	Hard
296	Best Meeting Point	Sort,Math	Hard
297	Serialize and Deserialize Binary Tree	Tree,Design	Hard
298	Binary Tree Longest Consecutive Sequence	Tree	Medium
299	Bulls and Cows	Hash Table	Easy
300	Longest Increasing Subsequence	Binary Search,Dynamic Programming	Medium
301	Remove Invalid Parentheses	Depth-first Search,Breadth-first Search	Hard
302	Smallest Rectangle Enclosing Black Pixels	Binary Search	Hard
303	Range Sum Query - Immutable	Dynamic Programming	Easy
304	Range Sum Query 2D - Immutable	Dynamic Programming	Medium
305	Number of Islands II	Union Find	Hard
306	Additive Number	Backtracking	Medium
307	Range Sum Query - Mutable	Binary Indexed Tree,Segment Tree	Medium
308	Range Sum Query 2D - Mutable	Binary Indexed Tree,Segment Tree	Hard
309	Best Time to Buy and Sell Stock with Cooldown	Dynamic Programming	Medium
310	Minimum Height Trees	Breadth-first Search,Graph	Medium
311	Sparse Matrix Multiplication	Hash Table	Medium
312	Burst Balloons	Divide and Conquer,Dynamic Programming	Hard
313	Super Ugly Number	Heap,Math	Medium
314	Binary Tree Vertical Order Traversal	Hash Table	Medium
315	Count of Smaller Numbers After Self	Sort,Binary Indexed Tree,Segment Tree,Binary Search,Divide and Conquer	Hard
316	Remove Duplicate Letters	Stack,Greedy	Hard
317	Shortest Distance from All Buildings	Breadth-first Search	Hard
318	Maximum Product of Word Lengths	Bit Manipulation	Medium
319	Bulb Switcher	Brainteaser,Math	Medium
320	Generalized Abbreviation	Bit Manipulation,Backtracking	Medium
321	Create Maximum Number	Greedy,Dynamic Programming	Hard
322	Coin Change	Dynamic Programming	Medium
323	Number of Connected Components in an Undirected Graph	Depth-first Search,Breadth-first Search,Union Find,Graph	Medium
324	Wiggle Sort II	Sort	Medium
325	Maximum Size Subarray Sum Equals k	Hash Table	Medium
326	Power of Three	Math	Easy
327	Count of Range Sum	Sort,Binary Indexed Tree,Segment Tree,Binary Search,Divide and Conquer	Hard
328	Odd Even Linked List	Linked List	Medium
329	Longest Increasing Path in a Matrix	Depth-first Search,Topological Sort,Memoization	Hard
330	Patching Array	Greedy	Hard
331	Verify Preorder Serialization of a Binary Tree	Stack	Medium
332	Reconstruct Itinerary	Depth-first Search,Graph	Medium
333	Largest BST Subtree	Tree	Medium
334	Increasing Triplet Subsequence		Medium
335	Self Crossing	Math	Hard
336	Palindrome Pairs	Trie,Hash Table,String	Hard
337	House Robber III	Tree,Depth-first Search	Medium
338	Counting Bits	Bit Manipulation,Dynamic Programming	Medium
339	Nested List Weight Sum	Depth-first Search	Easy
340	Longest Substring with At Most K Distinct Characters	Hash Table,String,Sliding Window	Hard
341	Flatten Nested List Iterator	Stack,Design	Medium
342	Power of Four	Bit Manipulation	Easy
343	Integer Break	Math,Dynamic Programming	Medium
344	Reverse String	Two Pointers,String	Easy
345	Reverse Vowels of a String	Two Pointers,String	Easy
346	Moving Average from Data Stream	Design,Queue	Easy
347	Top K Frequent Elements	Heap,Hash Table	Medium
348	Design Tic-Tac-Toe	Design	Medium
349	Intersection of Two Arrays	Sort,Hash Table,Two Pointers,Binary Search	Easy
350	Intersection of Two Arrays II	Sort,Hash Table,Two Pointers,Binary Search	Easy
351	Android Unlock Patterns	Dynamic Programming,Backtracking	Medium
352	Data Stream as Disjoint Intervals	Binary Search,Ordered Map	Hard
353	Design Snake Game	Design,Queue	Medium
354	Russian Doll Envelopes	Binary Search,Dynamic Programming	Hard
355	Design Twitter	Heap,Design,Hash Table	Medium
356	Line Reflection	Hash Table,Math	Medium
357	Count Numbers with Unique Digits	Math,Dynamic Programming,Backtracking	Medium
358	Rearrange String k Distance Apart	Heap,Greedy,Hash Table	Hard
359	Logger Rate Limiter	Design,Hash Table	Easy
360	Sort Transformed Array	Math,Two Pointers	Medium
361	Bomb Enemy	Dynamic Programming	Medium
362	Design Hit Counter	Design	Medium
363	Max Sum of Rectangle No Larger Than K	Queue,Binary Search,Dynamic Programming	Hard
364	Nested List Weight Sum II	Depth-first Search	Medium
365	Water and Jug Problem	Math	Medium
366	Find Leaves of Binary Tree	Tree,Depth-first Search	Medium
367	Valid Perfect Square	Math,Binary Search	Easy
368	Largest Divisible Subset	Math,Dynamic Programming	Medium
369	Plus One Linked List	Linked List	Medium
370	Range Addition	Array	Medium
371	Sum of Two Integers	Bit Manipulation	Easy
372	Super Pow	Math	Medium
373	Find K Pairs with Smallest Sums	Heap	Medium
374	Guess Number Higher or Lower	Binary Search	Easy
375	Guess Number Higher or Lower II	Minimax,Dynamic Programming	Medium
376	Wiggle Subsequence	Greedy,Dynamic Programming	Medium
377	Combination Sum IV	Dynamic Programming	Medium
378	Kth Smallest Element in a Sorted Matrix	Heap,Binary Search	Medium
379	Design Phone Directory	Design,Linked List	Medium
380	Insert Delete GetRandom O(1)	Design,Array,Hash Table	Medium
381	Insert Delete GetRandom O(1) - Duplicates allowed	Design,Array,Hash Table	Hard
382	Linked List Random Node	Reservoir Sampling	Medium
383	Ransom Note	String	Easy
384	Shuffle an Array		Medium
385	Mini Parser	Stack,String	Medium
386	Lexicographical Numbers		Medium
387	First Unique Character in a String	Hash Table,String	Easy
388	Longest Absolute File Path		Medium
389	Find the Difference	Bit Manipulation,Hash Table	Easy
390	Elimination Game		Medium
391	Perfect Rectangle	Line Sweep	Hard
392	Is Subsequence	Greedy,Binary Search,Dynamic Programming	Easy
393	UTF-8 Validation	Bit Manipulation	Medium
394	Decode String	Stack,Depth-first Search	Medium
395	Longest Substring with At Least K Repeating Characters		Medium
396	Rotate Function	Math	Medium
397	Integer Replacement	Bit Manipulation,Math	Medium
398	Random Pick Index	Reservoir Sampling	Medium
399	Evaluate Division	Union Find,Graph	Medium
400	Nth Digit	Math	Medium
401	Binary Watch	Bit Manipulation,Backtracking	Easy
402	Remove K Digits	Stack,Greedy	Medium
403	Frog Jump	Dynamic Programming	Hard
404	Sum of Left Leaves	Tree	Easy
405	Convert a Number to Hexadecimal	Bit Manipulation	Easy
406	Queue Reconstruction by Height	Greedy	Medium
407	Trapping Rain Water II	Heap,Breadth-first Search	Hard
408	Valid Word Abbreviation	String	Easy
409	Longest Palindrome	Hash Table	Easy
410	Split Array Largest Sum	Binary Search,Dynamic Programming	Hard
411	Minimum Unique Word Abbreviation	Bit Manipulation,Backtracking	Hard
412	Fizz Buzz		Easy
413	Arithmetic Slices	Math,Dynamic Programming	Medium
414	Third Maximum Number	Array	Easy
415	Add Strings	String	Easy
416	Partition Equal Subset Sum	Dynamic Programming	Medium
417	Pacific Atlantic Water Flow	Depth-first Search,Breadth-first Search	Medium
418	Sentence Screen Fitting	Dynamic Programming	Medium
419	Battleships in a Board		Medium
420	Strong Password Checker		Hard
421	Maximum XOR of Two Numbers in an Array	Bit Manipulation,Trie	Medium
422	Valid Word Square		Easy
423	Reconstruct Original Digits from English	Math	Medium
424	Longest Repeating Character Replacement	Two Pointers,Sliding Window	Medium
425	Word Squares	Trie,Backtracking	Hard
426	Convert Binary Search Tree to Sorted Doubly Linked List	Tree,Linked List,Divide and Conquer	Medium
427	Construct Quad Tree		Medium
428	Serialize and Deserialize N-ary Tree	Tree	Hard
429	N-ary Tree Level Order Traversal	Tree,Breadth-first Search	Medium
430	Flatten a Multilevel Doubly Linked List	Depth-first Search,Linked List	Medium
431	Encode N-ary Tree to Binary Tree	Tree	Hard
432	All O`one Data Structure	Design	Hard
433	Minimum Genetic Mutation		Medium
434	Number of Segments in a String	String	Easy
435	Non-overlapping Intervals	Greedy	Medium
436	Find Right Interval	Binary Search	Medium
437	Path Sum III	Tree	Easy
438	Find All Anagrams in a String	Hash Table	Medium
439	Ternary Expression Parser	Stack,Depth-first Search	Medium
440	K-th Smallest in Lexicographical Order		Hard
441	Arranging Coins	Math,Binary Search	Easy
442	Find All Duplicates in an Array	Array	Medium
443	String Compression	String	Easy
444	Sequence Reconstruction	Graph,Topological Sort	Medium
445	Add Two Numbers II	Linked List	Medium
446	Arithmetic Slices II - Subsequence	Dynamic Programming	Hard
447	Number of Boomerangs	Hash Table	Easy
448	Find All Numbers Disappeared in an Array	Array	Easy
449	Serialize and Deserialize BST	Tree	Medium
450	Delete Node in a BST	Tree	Medium
451	Sort Characters By Frequency	Heap,Hash Table	Medium
452	Minimum Number of Arrows to Burst Balloons	Greedy	Medium
453	Minimum Moves to Equal Array Elements	Math	Easy
454	4Sum II	Hash Table,Binary Search	Medium
455	Assign Cookies	Greedy	Easy
456	132 Pattern	Stack	Medium
457	Circular Array Loop	Array,Two Pointers	Medium
458	Poor Pigs	Math	Hard
459	Repeated Substring Pattern	String	Easy
460	LFU Cache	Design	Hard
461	Hamming Distance	Bit Manipulation	Easy
462	Minimum Moves to Equal Array Elements II	Math	Medium
463	Island Perimeter	Hash Table	Easy
464	Can I Win	Minimax,Dynamic Programming	Medium
465	Optimal Account Balancing		Hard
466	Count The Repetitions	Dynamic Programming	Hard
467	Unique Substrings in Wraparound String	Dynamic Programming	Medium
468	Validate IP Address	String	Medium
469	Convex Polygon	Math	Medium
470	Implement Rand10() Using Rand7()	Random,Rejection Sampling	Medium
471	Encode String with Shortest Length	Dynamic Programming	Hard
472	Concatenated Words	Depth-first Search,Trie,Dynamic Programming	Hard
473	Matchsticks to Square	Depth-first Search	Medium
474	Ones and Zeroes	Dynamic Programming	Medium
475	Heaters	Binary Search	Easy
476	Number Complement	Bit Manipulation	Easy
477	Total Hamming Distance	Bit Manipulation	Medium
478	Generate Random Point in a Circle	Math,Random,Rejection Sampling	Medium
479	Largest Palindrome Product		Hard
480	Sliding Window Median	Sliding Window	Hard
481	Magical String		Medium
482	License Key Formatting		Easy
483	Smallest Good Base	Math,Binary Search	Hard
484	Find Permutation	Greedy	Medium
485	Max Consecutive Ones	Array	Easy
486	Predict the Winner	Minimax,Dynamic Programming	Medium
487	Max Consecutive Ones II	Two Pointers	Medium
488	Zuma Game	Depth-first Search	Hard
489	Robot Room Cleaner	Depth-first Search	Hard
490	The Maze	Depth-first Search,Breadth-first Search	Medium
491	Increasing Subsequences	Depth-first Search	Medium
492	Construct the Rectangle		Easy
493	Reverse Pairs	Sort,Binary Indexed Tree,Segment Tree,Binary Search,Divide and Conquer	Hard
494	Target Sum	Depth-first Search,Dynamic Programming	Medium
495	Teemo Attacking	Array	Medium
496	Next Greater Element I	Stack	Easy
497	Random Point in Non-overlapping Rectangles	Binary Search,Random	Medium
498	Diagonal Traverse		Medium
499	The Maze III	Depth-first Search,Breadth-first Search	Hard
500	Keyboard Row	Hash Table	Easy
501	Find Mode in Binary Search Tree	Tree	Easy
502	IPO	Heap,Greedy	Hard
503	Next Greater Element II	Stack	Medium
504	Base 7		Easy
505	The Maze II	Depth-first Search,Breadth-first Search	Medium
506	Relative Ranks		Easy
507	Perfect Number	Math	Easy
508	Most Frequent Subtree Sum	Tree,Hash Table	Medium
509	Fibonacci Number	Array	Easy
510	Inorder Successor in BST II	Tree	Medium
511	Game Play Analysis I		Easy
512	Game Play Analysis II		Easy
513	Find Bottom Left Tree Value	Tree,Depth-first Search,Breadth-first Search	Medium
514	Freedom Trail	Depth-first Search,Divide and Conquer,Dynamic Programming	Hard
515	Find Largest Value in Each Tree Row	Tree,Depth-first Search,Breadth-first Search	Medium
516	Longest Palindromic Subsequence	Dynamic Programming	Medium
517	Super Washing Machines	Math,Dynamic Programming	Hard
518	Coin Change 2		Medium
519	Random Flip Matrix	Random	Medium
520	Detect Capital	String	Easy
521	Longest Uncommon Subsequence I	String	Easy
522	Longest Uncommon Subsequence II	String	Medium
523	Continuous Subarray Sum	Math,Dynamic Programming	Medium
524	Longest Word in Dictionary through Deleting	Sort,Two Pointers	Medium
525	Contiguous Array	Hash Table	Medium
526	Beautiful Arrangement	Backtracking	Medium
527	Word Abbreviation	Sort,String	Hard
528	Random Pick with Weight	Binary Search,Random	Medium
529	Minesweeper	Depth-first Search,Breadth-first Search	Medium
530	Minimum Absolute Difference in BST	Tree	Easy
531	Lonely Pixel I	Depth-first Search,Array	Medium
532	K-diff Pairs in an Array	Array,Two Pointers	Easy
533	Lonely Pixel II	Depth-first Search,Array	Medium
534	Game Play Analysis III		Medium
535	Encode and Decode TinyURL	Hash Table,Math	Medium
536	Construct Binary Tree from String	Tree,String	Medium
537	Complex Number Multiplication	Math,String	Medium
538	Convert BST to Greater Tree	Tree	Easy
539	Minimum Time Difference	String	Medium
540	Single Element in a Sorted Array		Medium
541	Reverse String II	String	Easy
542	01 Matrix	Depth-first Search,Breadth-first Search	Medium
543	Diameter of Binary Tree	Tree	Easy
544	Output Contest Matches	Recursion,String	Medium
545	Boundary of Binary Tree	Tree	Medium
546	Remove Boxes	Depth-first Search,Dynamic Programming	Hard
547	Friend Circles	Depth-first Search,Union Find	Medium
548	Split Array with Equal Sum	Array	Medium
549	Binary Tree Longest Consecutive Sequence II	Tree	Medium
550	Game Play Analysis IV		Medium
551	Student Attendance Record I	String	Easy
552	Student Attendance Record II	Dynamic Programming	Hard
553	Optimal Division	Math,String	Medium
554	Brick Wall	Hash Table	Medium
555	Split Concatenated Strings	String	Medium
556	Next Greater Element III	String	Medium
557	Reverse Words in a String III	String	Easy
558	Logical OR of Two Binary Grids Represented as Quad-Trees		Medium
559	Maximum Depth of N-ary Tree	Tree,Depth-first Search,Breadth-first Search	Easy
560	Subarray Sum Equals K	Array,Hash Table	Medium
561	Array Partition I	Array	Easy
562	Longest Line of Consecutive One in Matrix	Array	Medium
563	Binary Tree Tilt	Tree	Easy
564	Find the Closest Palindrome	String	Hard
565	Array Nesting	Array	Medium
566	Reshape the Matrix	Array	Easy
567	Permutation in String	Two Pointers,Sliding Window	Medium
568	Maximum Vacation Days	Dynamic Programming	Hard
569	Median Employee Salary		Hard
570	Managers with at Least 5 Direct Reports		Medium
571	Find Median Given Frequency of Numbers		Hard
572	Subtree of Another Tree	Tree	Easy
573	Squirrel Simulation	Math	Medium
574	Winning Candidate		Medium
575	Distribute Candies	Hash Table	Easy
576	Out of Boundary Paths	Depth-first Search,Dynamic Programming	Medium
577	Employee Bonus		Easy
578	Get Highest Answer Rate Question		Medium
579	Find Cumulative Salary of an Employee		Hard
580	Count Student Number in Departments		Medium
581	Shortest Unsorted Continuous Subarray	Array	Easy
582	Kill Process	Tree,Queue	Medium
583	Delete Operation for Two Strings	String	Medium
584	Find Customer Referee		Easy
585	Investments in 2016		Medium
586	Customer Placing the Largest Number of Orders		Easy
587	Erect the Fence	Geometry	Hard
588	Design In-Memory File System	Design	Hard
589	N-ary Tree Preorder Traversal	Tree	Easy
590	N-ary Tree Postorder Traversal	Tree	Easy
591	Tag Validator	Stack,String	Hard
592	Fraction Addition and Subtraction	Math	Medium
593	Valid Square	Math	Medium
594	Longest Harmonious Subsequence	Hash Table	Easy
595	Big Countries		Easy
596	Classes More Than 5 Students		Easy
597	Friend Requests I: Overall Acceptance Rate		Easy
598	Range Addition II	Math	Easy
599	Minimum Index Sum of Two Lists	Hash Table	Easy
600	Non-negative Integers without Consecutive Ones	Dynamic Programming	Hard
601	Human Traffic of Stadium		Hard
602	Friend Requests II: Who Has the Most Friends		Medium
603	Consecutive Available Seats		Easy
604	Design Compressed String Iterator	Design	Easy
605	Can Place Flowers	Array	Easy
606	Construct String from Binary Tree	Tree,String	Easy
607	Sales Person		Easy
608	Tree Node		Medium
609	Find Duplicate File in System	Hash Table,String	Medium
610	Triangle Judgement		Easy
611	Valid Triangle Number	Array	Medium
612	Shortest Distance in a Plane		Medium
613	Shortest Distance in a Line		Easy
614	Second Degree Follower		Medium
615	Average Salary: Departments VS Company		Hard
616	Add Bold Tag in String	String	Medium
617	Merge Two Binary Trees	Tree	Easy
618	Students Report By Geography		Hard
619	Biggest Single Number		Easy
620	Not Boring Movies		Easy
621	Task Scheduler	Greedy,Queue,Array	Medium
622	Design Circular Queue	Design,Queue	Medium
623	Add One Row to Tree	Tree	Medium
624	Maximum Distance in Arrays	Array,Hash Table	Easy
625	Minimum Factorization	Recursion,Math	Medium
626	Exchange Seats		Medium
627	Swap Salary		Easy
628	Maximum Product of Three Numbers	Array,Math	Easy
629	K Inverse Pairs Array	Dynamic Programming	Hard
630	Course Schedule III	Greedy	Hard
631	Design Excel Sum Formula	Design	Hard
632	Smallest Range Covering Elements from K Lists	Hash Table,Two Pointers,String	Hard
633	Sum of Square Numbers	Math	Easy
634	Find the Derangement of An Array	Math	Medium
635	Design Log Storage System	Design,String	Medium
636	Exclusive Time of Functions	Stack	Medium
637	Average of Levels in Binary Tree	Tree	Easy
638	Shopping Offers	Depth-first Search,Dynamic Programming	Medium
639	Decode Ways II	Dynamic Programming	Hard
640	Solve the Equation	Math	Medium
641	Design Circular Deque	Design,Queue	Medium
642	Design Search Autocomplete System	Design,Trie	Hard
643	Maximum Average Subarray I	Array	Easy
644	Maximum Average Subarray II	Array,Binary Search	Hard
645	Set Mismatch	Hash Table,Math	Easy
646	Maximum Length of Pair Chain	Dynamic Programming	Medium
647	Palindromic Substrings	String,Dynamic Programming	Medium
648	Replace Words	Trie,Hash Table	Medium
649	Dota2 Senate	Greedy	Medium
650	2 Keys Keyboard	Dynamic Programming	Medium
651	4 Keys Keyboard	Greedy,Math,Dynamic Programming	Medium
652	Find Duplicate Subtrees	Tree	Medium
653	Two Sum IV - Input is a BST	Tree	Easy
654	Maximum Binary Tree	Tree	Medium
655	Print Binary Tree	Tree	Medium
656	Coin Path	Dynamic Programming	Hard
657	Robot Return to Origin	String	Easy
658	Find K Closest Elements	Binary Search	Medium
659	Split Array into Consecutive Subsequences	Heap,Greedy	Medium
660	Remove 9	Math	Hard
661	Image Smoother	Array	Easy
662	Maximum Width of Binary Tree	Tree	Medium
663	Equal Tree Partition	Tree	Medium
664	Strange Printer	Depth-first Search,Dynamic Programming	Hard
665	Non-decreasing Array	Array	Easy
666	Path Sum IV	Tree	Medium
667	Beautiful Arrangement II	Array	Medium
668	Kth Smallest Number in Multiplication Table	Binary Search	Hard
669	Trim a Binary Search Tree	Tree	Easy
670	Maximum Swap	Array,Math	Medium
671	Second Minimum Node In a Binary Tree	Tree	Easy
672	Bulb Switcher II	Math	Medium
673	Number of Longest Increasing Subsequence	Dynamic Programming	Medium
674	Longest Continuous Increasing Subsequence	Array	Easy
675	Cut Off Trees for Golf Event	Breadth-first Search	Hard
676	Implement Magic Dictionary	Trie,Hash Table	Medium
677	Map Sum Pairs	Trie	Medium
678	Valid Parenthesis String	String	Medium
679	24 Game	Depth-first Search	Hard
680	Valid Palindrome II	String	Easy
681	Next Closest Time	String	Medium
682	Baseball Game	Stack	Easy
683	K Empty Slots	Ordered Map	Hard
684	Redundant Connection	Tree,Union Find,Graph	Medium
685	Redundant Connection II	Tree,Depth-first Search,Union Find,Graph	Hard
686	Repeated String Match	String	Easy
687	Longest Univalue Path	Tree,Recursion	Easy
688	Knight Probability in Chessboard	Dynamic Programming	Medium
689	Maximum Sum of 3 Non-Overlapping Subarrays	Array,Dynamic Programming	Hard
690	Employee Importance	Depth-first Search,Breadth-first Search,Hash Table	Easy
691	Stickers to Spell Word	Dynamic Programming,Backtracking	Hard
692	Top K Frequent Words	Heap,Trie,Hash Table	Medium
693	Binary Number with Alternating Bits	Bit Manipulation	Easy
694	Number of Distinct Islands	Depth-first Search,Hash Table	Medium
695	Max Area of Island	Depth-first Search,Array	Medium
696	Count Binary Substrings	String	Easy
697	Degree of an Array	Array	Easy
698	Partition to K Equal Sum Subsets	Recursion,Dynamic Programming	Medium
699	Falling Squares	Segment Tree,Ordered Map	Hard
700	Search in a Binary Search Tree	Tree	Easy
701	Insert into a Binary Search Tree	Tree	Medium
702	Search in a Sorted Array of Unknown Size	Binary Search	Medium
703	Kth Largest Element in a Stream	Heap	Easy
704	Binary Search	Binary Search	Easy
705	Design HashSet	Design,Hash Table	Easy
706	Design HashMap	Design,Hash Table	Easy
707	Design Linked List	Design,Linked List	Medium
708	Insert into a Sorted Circular Linked List	Linked List	Medium
709	To Lower Case	String	Easy
710	Random Pick with Blacklist	Sort,Hash Table,Binary Search,Random	Hard
711	Number of Distinct Islands II	Depth-first Search,Hash Table	Hard
712	Minimum ASCII Delete Sum for Two Strings	Dynamic Programming	Medium
713	Subarray Product Less Than K	Array,Two Pointers	Medium
714	Best Time to Buy and Sell Stock with Transaction Fee	Greedy,Array,Dynamic Programming	Medium
715	Range Module	Segment Tree,Ordered Map	Hard
716	Max Stack	Design	Easy
717	1-bit and 2-bit Characters	Array	Easy
718	Maximum Length of Repeated Subarray	Array,Hash Table,Binary Search,Dynamic Programming	Medium
719	Find K-th Smallest Pair Distance	Heap,Array,Binary Search	Hard
720	Longest Word in Dictionary	Trie,Hash Table	Easy
721	Accounts Merge	Depth-first Search,Union Find	Medium
722	Remove Comments	String	Medium
723	Candy Crush	Array,Two Pointers	Medium
724	Find Pivot Index	Array	Easy
725	Split Linked List in Parts	Linked List	Medium
726	Number of Atoms	Stack,Recursion,Hash Table	Hard
727	Minimum Window Subsequence	Dynamic Programming,Sliding Window	Hard
728	Self Dividing Numbers	Math	Easy
729	My Calendar I	Array	Medium
730	Count Different Palindromic Subsequences	String,Dynamic Programming	Hard
731	My Calendar II	Ordered Map	Medium
732	My Calendar III	Segment Tree,Ordered Map	Hard
733	Flood Fill	Depth-first Search	Easy
734	Sentence Similarity	Hash Table	Easy
735	Asteroid Collision	Stack	Medium
736	Parse Lisp Expression	String	Hard
737	Sentence Similarity II	Depth-first Search,Union Find	Medium
738	Monotone Increasing Digits	Greedy	Medium
739	Daily Temperatures	Stack,Hash Table	Medium
740	Delete and Earn	Dynamic Programming	Medium
741	Cherry Pickup	Dynamic Programming	Hard
742	Closest Leaf in a Binary Tree	Tree	Medium
743	Network Delay Time	Heap,Depth-first Search,Breadth-first Search,Graph	Medium
744	Find Smallest Letter Greater Than Target	Binary Search	Easy
745	Prefix and Suffix Search	Trie	Hard
746	Min Cost Climbing Stairs	Array,Dynamic Programming	Easy
747	Largest Number At Least Twice of Others	Array	Easy
748	Shortest Completing Word	Hash Table	Easy
749	Contain Virus	Depth-first Search	Hard
750	Number Of Corner Rectangles	Dynamic Programming	Medium
751	IP to CIDR	Bit Manipulation	Easy
752	Open the Lock	Breadth-first Search	Medium
753	Cracking the Safe	Depth-first Search,Math	Hard
754	Reach a Number	Math	Medium
755	Pour Water	Array	Medium
756	Pyramid Transition Matrix	Bit Manipulation,Depth-first Search	Medium
757	Set Intersection Size At Least Two	Greedy	Hard
758	Bold Words in String	String	Easy
759	Employee Free Time	Heap,Greedy	Hard
760	Find Anagram Mappings	Hash Table	Easy
761	Special Binary String	Recursion,String	Hard
762	Prime Number of Set Bits in Binary Representation	Bit Manipulation	Easy
763	Partition Labels	Greedy,Two Pointers	Medium
764	Largest Plus Sign	Dynamic Programming	Medium
765	Couples Holding Hands	Greedy,Union Find,Graph	Hard
766	Toeplitz Matrix	Array	Easy
767	Reorganize String	Heap,Greedy,Sort,String	Medium
768	Max Chunks To Make Sorted II	Array	Hard
769	Max Chunks To Make Sorted	Array	Medium
770	Basic Calculator IV	Stack,Hash Table,String	Hard
771	Jewels and Stones	Hash Table	Easy
772	Basic Calculator III	Stack,String	Hard
773	Sliding Puzzle	Breadth-first Search	Hard
774	Minimize Max Distance to Gas Station	Binary Search	Hard
775	Global and Local Inversions	Array,Math	Medium
776	Split BST	Tree,Recursion	Medium
777	Swap Adjacent in LR String	Brainteaser	Medium
778	Swim in Rising Water	Heap,Depth-first Search,Union Find,Binary Search	Hard
779	K-th Symbol in Grammar	Recursion	Medium
780	Reaching Points	Math	Hard
781	Rabbits in Forest	Hash Table,Math	Medium
782	Transform to Chessboard	Array,Math	Hard
783	Minimum Distance Between BST Nodes	Tree,Recursion	Easy
784	Letter Case Permutation	Bit Manipulation,Backtracking	Easy
785	Is Graph Bipartite?	Depth-first Search,Breadth-first Search,Graph	Medium
786	K-th Smallest Prime Fraction	Heap,Binary Search	Hard
787	Cheapest Flights Within K Stops	Heap,Breadth-first Search,Dynamic Programming	Medium
788	Rotated Digits	String	Easy
789	Escape The Ghosts	Math	Medium
790	Domino and Tromino Tiling	Dynamic Programming	Medium
791	Custom Sort String	String	Medium
792	Number of Matching Subsequences	Array	Medium
793	Preimage Size of Factorial Zeroes Function	Binary Search	Hard
794	Valid Tic-Tac-Toe State	Recursion,Math	Medium
795	Number of Subarrays with Bounded Maximum	Array	Medium
796	Rotate String		Easy
797	All Paths From Source to Target		Medium
798	Smallest Rotation with Highest Score		Hard
799	Champagne Tower		Medium
800	Similar RGB Color	Math,String	Easy
801	Minimum Swaps To Make Sequences Increasing	Dynamic Programming	Medium
802	Find Eventual Safe States	Depth-first Search,Graph	Medium
803	Bricks Falling When Hit	Union Find	Hard
804	Unique Morse Code Words	String	Easy
805	Split Array With Same Average	Math	Hard
806	Number of Lines To Write String		Easy
807	Max Increase to Keep City Skyline		Medium
808	Soup Servings	Dynamic Programming	Medium
809	Expressive Words	String	Medium
810	Chalkboard XOR Game	Math	Hard
811	Subdomain Visit Count	Hash Table	Easy
812	Largest Triangle Area	Math	Easy
813	Largest Sum of Averages	Dynamic Programming	Medium
814	Binary Tree Pruning	Tree	Medium
815	Bus Routes	Breadth-first Search	Hard
816	Ambiguous Coordinates	String	Medium
817	Linked List Components	Linked List	Medium
818	Race Car	Heap,Dynamic Programming	Hard
819	Most Common Word	String	Easy
820	Short Encoding of Words		Medium
821	Shortest Distance to a Character		Easy
822	Card Flipping Game		Medium
823	Binary Trees With Factors		Medium
824	Goat Latin	String	Easy
825	Friends Of Appropriate Ages	Array	Medium
826	Most Profit Assigning Work	Two Pointers	Medium
827	Making A Large Island	Depth-first Search	Hard
828	Count Unique Characters of All Substrings of a Given String	Two Pointers	Hard
829	Consecutive Numbers Sum	Math	Hard
830	Positions of Large Groups	Array	Easy
831	Masking Personal Information	String	Medium
832	Flipping an Image	Array	Easy
833	Find And Replace in String	String	Medium
834	Sum of Distances in Tree	Tree,Depth-first Search	Hard
835	Image Overlap	Array	Medium
836	Rectangle Overlap	Math	Easy
837	New 21 Game	Dynamic Programming	Medium
838	Push Dominoes	Two Pointers,Dynamic Programming	Medium
839	Similar String Groups	Depth-first Search,Union Find,Graph	Hard
840	Magic Squares In Grid	Array	Easy
841	Keys and Rooms	Depth-first Search,Graph	Medium
842	Split Array into Fibonacci Sequence	Greedy,String,Backtracking	Medium
843	Guess the Word	Minimax	Hard
844	Backspace String Compare	Stack,Two Pointers	Easy
845	Longest Mountain in Array	Two Pointers	Medium
846	Hand of Straights	Ordered Map	Medium
847	Shortest Path Visiting All Nodes	Breadth-first Search,Dynamic Programming	Hard
848	Shifting Letters	String	Medium
849	Maximize Distance to Closest Person	Array	Easy
850	Rectangle Area II	Segment Tree,Line Sweep	Hard
851	Loud and Rich	Depth-first Search	Medium
852	Peak Index in a Mountain Array	Binary Search	Easy
853	Car Fleet	Sort	Medium
854	K-Similar Strings	Breadth-first Search,Graph	Hard
855	Exam Room	Ordered Map	Medium
856	Score of Parentheses	Stack,String	Medium
857	Minimum Cost to Hire K Workers	Heap	Hard
858	Mirror Reflection	Math	Medium
859	Buddy Strings	String	Easy
860	Lemonade Change	Greedy	Easy
861	Score After Flipping Matrix	Greedy	Medium
862	Shortest Subarray with Sum at Least K	Queue,Binary Search	Hard
863	All Nodes Distance K in Binary Tree	Tree,Depth-first Search,Breadth-first Search	Medium
864	Shortest Path to Get All Keys	Heap,Breadth-first Search	Hard
865	Smallest Subtree with all the Deepest Nodes	Tree	Medium
866	Prime Palindrome	Math	Medium
867	Transpose Matrix	Array	Easy
868	Binary Gap	Math	Easy
869	Reordered Power of 2	Math	Medium
870	Advantage Shuffle	Greedy,Array	Medium
871	Minimum Number of Refueling Stops	Heap,Dynamic Programming	Hard
872	Leaf-Similar Trees	Tree,Depth-first Search	Easy
873	Length of Longest Fibonacci Subsequence	Array,Dynamic Programming	Medium
874	Walking Robot Simulation	Greedy	Easy
875	Koko Eating Bananas	Binary Search	Medium
876	Middle of the Linked List	Linked List	Easy
877	Stone Game	Minimax,Math,Dynamic Programming	Medium
878	Nth Magical Number	Math,Binary Search	Hard
879	Profitable Schemes	Dynamic Programming	Hard
880	Decoded String at Index	Stack	Medium
881	Boats to Save People	Greedy,Two Pointers	Medium
882	Reachable Nodes In Subdivided Graph	Heap	Hard
883	Projection Area of 3D Shapes	Math	Easy
884	Uncommon Words from Two Sentences	Hash Table	Easy
885	Spiral Matrix III	Math	Medium
886	Possible Bipartition	Depth-first Search	Medium
887	Super Egg Drop	Math,Binary Search,Dynamic Programming	Hard
888	Fair Candy Swap	Array	Easy
889	Construct Binary Tree from Preorder and Postorder Traversal	Tree	Medium
890	Find and Replace Pattern	String	Medium
891	Sum of Subsequence Widths	Array,Math	Hard
892	Surface Area of 3D Shapes	Geometry,Math	Easy
893	Groups of Special-Equivalent Strings	String	Easy
894	All Possible Full Binary Trees	Tree,Recursion	Medium
895	Maximum Frequency Stack	Stack,Hash Table	Hard
896	Monotonic Array	Array	Easy
897	Increasing Order Search Tree	Tree,Depth-first Search	Easy
898	Bitwise ORs of Subarrays	Bit Manipulation,Dynamic Programming	Medium
899	Orderly Queue	Math,String	Hard
900	RLE Iterator	Array	Medium
901	Online Stock Span	Stack	Medium
902	Numbers At Most N Given Digit Set	Math,Dynamic Programming	Hard
903	Valid Permutations for DI Sequence	Divide and Conquer,Dynamic Programming	Hard
904	Fruit Into Baskets	Two Pointers	Medium
905	Sort Array By Parity	Array	Easy
906	Super Palindromes	Math	Hard
907	Sum of Subarray Minimums	Stack,Array	Medium
908	Smallest Range I	Math	Easy
909	Snakes and Ladders	Breadth-first Search	Medium
910	Smallest Range II	Greedy,Math	Medium
911	Online Election	Binary Search	Medium
912	Sort an Array		Medium
913	Cat and Mouse	Breadth-first Search,Minimax	Hard
914	X of a Kind in a Deck of Cards	Array,Math	Easy
915	Partition Array into Disjoint Intervals	Array	Medium
916	Word Subsets	String	Medium
917	Reverse Only Letters	String	Easy
918	Maximum Sum Circular Subarray	Array	Medium
919	Complete Binary Tree Inserter	Tree	Medium
920	Number of Music Playlists	Dynamic Programming	Hard
921	Minimum Add to Make Parentheses Valid	Stack,Greedy	Medium
922	Sort Array By Parity II	Sort,Array	Easy
923	3Sum With Multiplicity	Two Pointers	Medium
924	Minimize Malware Spread	Depth-first Search,Union Find	Hard
925	Long Pressed Name	Two Pointers,String	Easy
926	Flip String to Monotone Increasing	Array	Medium
927	Three Equal Parts	Greedy,Math,Binary Search	Hard
928	Minimize Malware Spread II	Depth-first Search,Union Find,Graph	Hard
929	Unique Email Addresses	String	Easy
930	Binary Subarrays With Sum	Hash Table,Two Pointers	Medium
931	Minimum Falling Path Sum	Dynamic Programming	Medium
932	Beautiful Array	Divide and Conquer	Medium
933	Number of Recent Calls	Queue	Easy
934	Shortest Bridge	Depth-first Search,Breadth-first Search	Medium
935	Knight Dialer	Dynamic Programming	Medium
936	Stamping The Sequence	Greedy,String	Hard
937	Reorder Data in Log Files	String	Easy
938	Range Sum of BST	Tree,Recursion	Easy
939	Minimum Area Rectangle	Hash Table	Medium
940	Distinct Subsequences II	Dynamic Programming	Hard
941	Valid Mountain Array	Array	Easy
942	DI String Match	Math	Easy
943	Find the Shortest Superstring	Dynamic Programming	Hard
944	Delete Columns to Make Sorted	Greedy	Easy
945	Minimum Increment to Make Array Unique	Array	Medium
946	Validate Stack Sequences	Stack	Medium
947	Most Stones Removed with Same Row or Column	Depth-first Search,Union Find	Medium
948	Bag of Tokens	Greedy	Medium
949	Largest Time for Given Digits	Math	Easy
950	Reveal Cards In Increasing Order	Array	Medium
951	Flip Equivalent Binary Trees	Tree	Medium
952	Largest Component Size by Common Factor	Union Find,Math	Hard
953	Verifying an Alien Dictionary	Hash Table	Easy
954	Array of Doubled Pairs	Array,Hash Table	Medium
955	Delete Columns to Make Sorted II	Greedy	Medium
956	Tallest Billboard	Dynamic Programming	Hard
957	Prison Cells After N Days	Hash Table	Medium
958	Check Completeness of a Binary Tree	Tree	Medium
959	Regions Cut By Slashes	Depth-first Search,Union Find,Graph	Medium
960	Delete Columns to Make Sorted III	Dynamic Programming	Hard
961	N-Repeated Element in Size 2N Array	Hash Table	Easy
962	Maximum Width Ramp	Array	Medium
963	Minimum Area Rectangle II	Geometry,Math	Medium
964	Least Operators to Express Number	Math,Dynamic Programming	Hard
965	Univalued Binary Tree	Tree	Easy
966	Vowel Spellchecker	Hash Table,String	Medium
967	Numbers With Same Consecutive Differences	Dynamic Programming	Medium
968	Binary Tree Cameras	Tree,Depth-first Search,Dynamic Programming	Hard
969	Pancake Sorting	Sort,Array	Medium
970	Powerful Integers	Hash Table,Math	Easy
971	Flip Binary Tree To Match Preorder Traversal	Tree,Depth-first Search	Medium
972	Equal Rational Numbers	Math	Hard
973	K Closest Points to Origin	Heap,Sort,Divide and Conquer	Medium
974	Subarray Sums Divisible by K	Array,Hash Table	Medium
975	Odd Even Jump	Stack,Dynamic Programming,Ordered Map	Hard
976	Largest Perimeter Triangle	Sort,Math	Easy
977	Squares of a Sorted Array	Array,Two Pointers	Easy
978	Longest Turbulent Subarray	Array,Dynamic Programming,Sliding Window	Medium
979	Distribute Coins in Binary Tree	Tree,Depth-first Search	Medium
980	Unique Paths III	Depth-first Search,Backtracking	Hard
981	Time Based Key-Value Store	Hash Table,Binary Search	Medium
982	Triples with Bitwise AND Equal To Zero	Dynamic Programming	Hard
983	Minimum Cost For Tickets	Dynamic Programming	Medium
984	String Without AAA or BBB	Greedy	Medium
985	Sum of Even Numbers After Queries	Array	Easy
986	Interval List Intersections	Two Pointers	Medium
987	Vertical Order Traversal of a Binary Tree	Tree,Hash Table	Medium
988	Smallest String Starting From Leaf	Tree,Depth-first Search	Medium
989	Add to Array-Form of Integer	Array	Easy
990	Satisfiability of Equality Equations	Union Find,Graph	Medium
991	Broken Calculator	Greedy,Math	Medium
992	Subarrays with K Different Integers	Hash Table,Two Pointers,Sliding Window	Hard
993	Cousins in Binary Tree	Tree,Breadth-first Search	Easy
994	Rotting Oranges	Breadth-first Search	Easy
995	Minimum Number of K Consecutive Bit Flips	Greedy,Sliding Window	Hard
996	Number of Squareful Arrays	Graph,Math,Backtracking	Hard
997	Find the Town Judge	Graph	Easy
998	Maximum Binary Tree II	Tree	Medium
999	Available Captures for Rook	Array	Easy
1000	Minimum Cost to Merge Stones	Dynamic Programming	Hard
1001	Grid Illumination	Hash Table	Hard
1002	Find Common Characters	Array,Hash Table	Easy
1003	Check If Word Is Valid After Substitutions	Stack,String	Medium
1004	Max Consecutive Ones III	Two Pointers,Sliding Window	Medium
1005	Maximize Sum Of Array After K Negations	Greedy	Easy
1006	Clumsy Factorial	Math	Medium
1007	Minimum Domino Rotations For Equal Row	Greedy,Array	Medium
1008	Construct Binary Search Tree from Preorder Traversal	Tree	Medium
1009	Complement of Base 10 Integer	Math	Easy
1010	Pairs of Songs With Total Durations Divisible by 60	Array	Easy
1011	Capacity To Ship Packages Within D Days	Array,Binary Search	Medium
1012	Numbers With Repeated Digits	Math,Dynamic Programming	Hard
1013	Partition Array Into Three Parts With Equal Sum	Array	Easy
1014	Best Sightseeing Pair	Array	Medium
1015	Smallest Integer Divisible by K	Math	Medium
1016	Binary String With Substrings Representing 1 To N	String	Medium
1017	Convert to Base -2	Math	Medium
1018	Binary Prefix Divisible By 5	Array	Easy
1019	Next Greater Node In Linked List	Stack,Linked List	Medium
1020	Number of Enclaves	Depth-first Search	Medium
1021	Remove Outermost Parentheses	Stack	Easy
1022	Sum of Root To Leaf Binary Numbers	Tree	Easy
1023	Camelcase Matching	Trie,String	Medium
1024	Video Stitching	Dynamic Programming	Medium
1025	Divisor Game	Math,Dynamic Programming	Easy
1026	Maximum Difference Between Node and Ancestor	Tree,Depth-first Search	Medium
1027	Longest Arithmetic Sequence	Dynamic Programming	Medium
1028	Recover a Tree From Preorder Traversal	Tree,Depth-first Search	Hard
1029	Two City Scheduling	Greedy	Easy
1030	Matrix Cells in Distance Order	Sort	Easy
1031	Maximum Sum of Two Non-Overlapping Subarrays	Array	Medium
1032	Stream of Characters	Trie	Hard
1033	Moving Stones Until Consecutive	Brainteaser	Easy
1034	Coloring A Border	Depth-first Search	Medium
1035	Uncrossed Lines	Array	Medium
1036	Escape a Large Maze	Breadth-first Search	Hard
1037	Valid Boomerang	Math	Easy
1038	Binary Search Tree to Greater Sum Tree	Binary Search Tree	Medium
1039	Minimum Score Triangulation of Polygon	Dynamic Programming	Medium
1040	Moving Stones Until Consecutive II	Array,Sliding Window	Medium
1041	Robot Bounded In Circle	Math	Medium
1042	Flower Planting With No Adjacent	Graph	Easy
1043	Partition Array for Maximum Sum	Graph	Medium
1044	Longest Duplicate Substring	Hash Table,Binary Search	Hard
1045	Customers Who Bought All Products		Medium
1046	Last Stone Weight	Heap,Greedy	Easy
1047	Remove All Adjacent Duplicates In String	Stack	Easy
1048	Longest String Chain	Hash Table,Dynamic Programming	Medium
1049	Last Stone Weight II	Dynamic Programming	Medium
1050	Actors and Directors Who Cooperated At Least Three Times		Easy
1051	Height Checker	Array	Easy
1052	Grumpy Bookstore Owner	Array,Sliding Window	Medium
1053	Previous Permutation With One Swap	Greedy,Array	Medium
1054	Distant Barcodes	Heap,Sort	Medium
1055	Shortest Way to Form String	Greedy,Dynamic Programming	Medium
1056	Confusing Number	Math	Easy
1057	Campus Bikes	Greedy,Sort	Medium
1058	Minimize Rounding Error to Meet Target	Greedy,Math,Dynamic Programming	Medium
1059	All Paths from Source Lead to Destination	Depth-first Search,Graph	Medium
1060	Missing Element in Sorted Array	Binary Search	Medium
1061	Lexicographically Smallest Equivalent String	Depth-first Search,Union Find	Medium
1062	Longest Repeating Substring	String	Medium
1063	Number of Valid Subarrays	Stack	Hard
1064	Fixed Point	Array,Binary Search	Easy
1065	Index Pairs of a String	Trie,String	Easy
1066	Campus Bikes II	Dynamic Programming,Backtracking	Medium
1067	Digit Count in Range	Math,Dynamic Programming	Hard
1068	Product Sales Analysis I		Easy
1069	Product Sales Analysis II		Easy
1070	Product Sales Analysis III		Medium
1071	Greatest Common Divisor of Strings	String	Easy
1072	Flip Columns For Maximum Number of Equal Rows	Hash Table	Medium
1073	Adding Two Negabinary Numbers	Math	Medium
1074	Number of Submatrices That Sum to Target	Array,Dynamic Programming,Sliding Window	Hard
1075	Project Employees I		Easy
1076	Project Employees II		Easy
1077	Project Employees III		Medium
1078	Occurrences After Bigram	Hash Table	Easy
1079	Letter Tile Possibilities	Backtracking	Medium
1080	Insufficient Nodes in Root to Leaf Paths	Depth-first Search	Medium
1081	Smallest Subsequence of Distinct Characters	String	Medium
1082	Sales Analysis I		Easy
1083	Sales Analysis II		Easy
1084	Sales Analysis III		Easy
1085	Sum of Digits in the Minimum Number	Array	Easy
1086	High Five	Sort,Array,Hash Table	Easy
1087	Brace Expansion	Backtracking	Medium
1088	Confusing Number II	Math,Backtracking	Hard
1089	Duplicate Zeros	Array	Easy
1090	Largest Values From Labels	Greedy,Hash Table	Medium
1091	Shortest Path in Binary Matrix	Breadth-first Search	Medium
1092	Shortest Common Supersequence	Dynamic Programming	Hard
1093	Statistics from a Large Sample	Math,Two Pointers	Medium
1094	Car Pooling	Greedy	Medium
1095	Find in Mountain Array	Binary Search	Hard
1096	Brace Expansion II	String	Hard
1097	Game Play Analysis V		Hard
1098	Unpopular Books		Medium
1099	Two Sum Less Than K	Array	Easy
1100	Find K-Length Substrings With No Repeated Characters	String,Sliding Window	Medium
1101	The Earliest Moment When Everyone Become Friends	Union Find	Medium
1102	Path With Maximum Minimum Value	Depth-first Search,Union Find,Graph	Medium
1103	Distribute Candies to People	Math	Easy
1104	Path In Zigzag Labelled Binary Tree	Tree,Math	Medium
1105	Filling Bookcase Shelves	Dynamic Programming	Medium
1106	Parsing A Boolean Expression	String	Hard
1107	New Users Daily Count		Medium
1108	Defanging an IP Address	String	Easy
1109	Corporate Flight Bookings	Array,Math	Medium
1110	Delete Nodes And Return Forest	Tree,Depth-first Search	Medium
1111	Maximum Nesting Depth of Two Valid Parentheses Strings	Greedy,Binary Search	Medium
1112	Highest Grade For Each Student		Medium
1113	Reported Posts		Easy
1114	Print in Order		Easy
1115	Print FooBar Alternately		Medium
1116	Print Zero Even Odd		Medium
1117	Building H2O		Medium
1118	Number of Days in a Month		Easy
1119	Remove Vowels from a String	String	Easy
1120	Maximum Average Subtree	Tree	Medium
1121	Divide Array Into Increasing Sequences	Math	Hard
1122	Relative Sort Array	Sort,Array	Easy
1123	Lowest Common Ancestor of Deepest Leaves	Tree,Depth-first Search	Medium
1124	Longest Well-Performing Interval	Stack	Medium
1125	Smallest Sufficient Team	Bit Manipulation,Dynamic Programming	Hard
1126	Active Businesses		Medium
1127	User Purchase Platform		Hard
1128	Number of Equivalent Domino Pairs	Array	Easy
1129	Shortest Path with Alternating Colors	Breadth-first Search,Graph	Medium
1130	Minimum Cost Tree From Leaf Values	Stack,Tree,Dynamic Programming	Medium
1131	Maximum of Absolute Value Expression	Bit Manipulation,Math	Medium
1132	Reported Posts II		Medium
1133	Largest Unique Number	Array,Hash Table	Easy
1134	Armstrong Number	Math	Easy
1135	Connecting Cities With Minimum Cost	Union Find,Graph	Medium
1136	Parallel Courses	Depth-first Search,Graph,Dynamic Programming	Hard
1137	N-th Tribonacci Number	Recursion	Easy
1138	Alphabet Board Path	Hash Table,String	Medium
1139	Largest 1-Bordered Square	Dynamic Programming	Medium
1140	Stone Game II	Dynamic Programming	Medium
1141	User Activity for the Past 30 Days I		Easy
1142	User Activity for the Past 30 Days II		Easy
1143	Longest Common Subsequence	Dynamic Programming	Medium
1144	Decrease Elements To Make Array Zigzag	Array	Medium
1145	Binary Tree Coloring Game	Tree,Depth-first Search	Medium
1146	Snapshot Array	Array	Medium
1147	Longest Chunked Palindrome Decomposition	Dynamic Programming	Hard
1148	Article Views I		Easy
1149	Article Views II		Medium
1150	Check If a Number Is Majority Element in a Sorted Array	Array,Binary Search	Easy
1151	Minimum Swaps to Group All 1's Together	Array,Sliding Window	Medium
1152	Analyze User Website Visit Pattern	Sort,Array,Hash Table	Medium
1153	String Transforms Into Another String	Graph	Hard
1154	Day of the Year	Math	Easy
1155	Number of Dice Rolls With Target Sum	Dynamic Programming	Medium
1156	Swap For Longest Repeated Character Substring	String	Medium
1157	Online Majority Element In Subarray	Segment Tree,Array,Binary Search	Hard
1158	Market Analysis I		Medium
1159	Market Analysis II		Hard
1160	Find Words That Can Be Formed by Characters	Array,Hash Table	Easy
1161	Maximum Level Sum of a Binary Tree	Graph	Medium
1162	As Far from Land as Possible	Breadth-first Search,Graph	Medium
1163	Last Substring in Lexicographical Order	String	Hard
1164	Product Price at a Given Date		Medium
1165	Single-Row Keyboard	String	Easy
1166	Design File System	Design,Hash Table	Medium
1167	Minimum Cost to Connect Sticks	Greedy	Medium
1168	Optimize Water Distribution in a Village	Union Find,Graph	Hard
1169	Invalid Transactions	Array,String	Medium
1170	Compare Strings by Frequency of the Smallest Character	Array,String	Easy
1171	Remove Zero Sum Consecutive Nodes from Linked List	Linked List	Medium
1172	Dinner Plate Stacks	Design	Hard
1173	Immediate Food Delivery I		Easy
1174	Immediate Food Delivery II		Medium
1175	Prime Arrangements	Math	Easy
1176	Diet Plan Performance	Array,Sliding Window	Easy
1177	Can Make Palindrome from Substring	Array,String	Medium
1178	Number of Valid Words for Each Puzzle	Bit Manipulation,Hash Table	Hard
1179	Reformat Department Table		Easy
1180	Count Substrings with Only One Distinct Letter	Math,String	Easy
1181	Before and After Puzzle	String	Medium
1182	Shortest Distance to Target Color	Binary Search	Medium
1183	Maximum Number of Ones	Sort,Math	Hard
1184	Distance Between Bus Stops	Array	Easy
1185	Day of the Week	Array	Easy
1186	Maximum Subarray Sum with One Deletion	Dynamic Programming	Medium
1187	Make Array Strictly Increasing	Dynamic Programming	Hard
1188	Design Bounded Blocking Queue		Medium
1189	Maximum Number of Balloons	Hash Table,String	Easy
1190	Reverse Substrings Between Each Pair of Parentheses	Stack	Medium
1191	K-Concatenation Maximum Sum	Dynamic Programming	Medium
1192	Critical Connections in a Network	Depth-first Search	Hard
1193	Monthly Transactions I		Medium
1194	Tournament Winners		Hard
1195	Fizz Buzz Multithreaded		Medium
1196	How Many Apples Can You Put into the Basket	Greedy	Easy
1197	Minimum Knight Moves	Breadth-first Search	Medium
1198	Find Smallest Common Element in All Rows	Hash Table,Binary Search	Medium
1199	Minimum Time to Build Blocks	Math,Dynamic Programming	Hard
1200	Minimum Absolute Difference	Array	Easy
1201	Ugly Number III	Math,Binary Search	Medium
1202	Smallest String With Swaps	Union Find,Array	Medium
1203	Sort Items by Groups Respecting Dependencies	Depth-first Search,Graph,Topological Sort	Hard
1204	Last Person to Fit in the Elevator		Medium
1205	Monthly Transactions II		Medium
1206	Design Skiplist	Design	Hard
1207	Unique Number of Occurrences	Hash Table	Easy
1208	Get Equal Substrings Within Budget	Array,Sliding Window	Medium
1209	Remove All Adjacent Duplicates in String II	Stack	Medium
1210	Minimum Moves to Reach Target with Rotations	Breadth-first Search	Hard
1211	Queries Quality and Percentage		Easy
1212	Team Scores in Football Tournament		Medium
1213	Intersection of Three Sorted Arrays	Hash Table,Two Pointers	Easy
1214	Two Sum BSTs	Binary Search Tree	Medium
1215	Stepping Numbers	Backtracking	Medium
1216	Valid Palindrome III	String,Dynamic Programming	Hard
1217	Play with Chips	Greedy,Array,Math	Easy
1218	Longest Arithmetic Subsequence of Given Difference	Math,Dynamic Programming	Medium
1219	Path with Maximum Gold	Backtracking	Medium
1220	Count Vowels Permutation	Dynamic Programming	Hard
1221	Split a String in Balanced Strings	Greedy,String	Easy
1222	Queens That Can Attack the King	Array	Medium
1223	Dice Roll Simulation	Dynamic Programming	Medium
1224	Maximum Equal Frequency	Hash Table	Hard
1225	Report Contiguous Dates		Hard
1226	The Dining Philosophers		Medium
1227	Airplane Seat Assignment Probability	Brainteaser,Math,Dynamic Programming	Medium
1228	Missing Number In Arithmetic Progression	Math	Easy
1229	Meeting Scheduler	Line Sweep	Medium
1230	Toss Strange Coins	Math,Dynamic Programming	Medium
1231	Divide Chocolate	Greedy,Binary Search	Hard
1232	Check If It Is a Straight Line	Geometry,Array,Math	Easy
1233	Remove Sub-Folders from the Filesystem	Array,String	Medium
1234	Replace the Substring for Balanced String	Two Pointers,String	Medium
1235	Maximum Profit in Job Scheduling	Sort,Binary Search,Dynamic Programming	Hard
1236	Web Crawler	Depth-first Search,Breadth-first Search	Medium
1237	Find Positive Integer Solution for a Given Equation	Math,Binary Search	Easy
1238	Circular Permutation in Binary Representation	Math	Medium
1239	Maximum Length of a Concatenated String with Unique Characters	Bit Manipulation,Backtracking	Medium
1240	Tiling a Rectangle with the Fewest Squares	Dynamic Programming,Backtracking	Hard
1241	Number of Comments per Post		Easy
1242	Web Crawler Multithreaded	Depth-first Search,Breadth-first Search	Medium
1243	Array Transformation	Array	Easy
1244	Design A Leaderboard	Sort,Design,Hash Table	Medium
1245	Tree Diameter	Tree,Depth-first Search,Breadth-first Search	Medium
1246	Palindrome Removal	Dynamic Programming	Hard
1247	Minimum Swaps to Make Strings Equal	Greedy,String	Medium
1248	Count Number of Nice Subarrays	Two Pointers	Medium
1249	Minimum Remove to Make Valid Parentheses	Stack,String	Medium
1250	Check If It Is a Good Array	Math	Hard
1251	Average Selling Price		Easy
1252	Cells with Odd Values in a Matrix	Array	Easy
1253	Reconstruct a 2-Row Binary Matrix	Greedy,Math	Medium
1254	Number of Closed Islands	Depth-first Search	Medium
1255	Maximum Score Words Formed by Letters	Bit Manipulation	Hard
1256	Encode Number	Bit Manipulation,Math	Medium
1257	Smallest Common Region	Tree	Medium
1258	Synonymous Sentences	Backtracking	Medium
1259	Handshakes That Don't Cross	Math,Dynamic Programming	Hard
1260	Shift 2D Grid	Array	Easy
1261	Find Elements in a Contaminated Binary Tree	Tree,Hash Table	Medium
1262	Greatest Sum Divisible by Three	Dynamic Programming	Medium
1263	Minimum Moves to Move a Box to Their Target Location	Breadth-first Search	Hard
1264	Page Recommendations		Medium
1265	Print Immutable Linked List in Reverse		Medium
1266	Minimum Time Visiting All Points	Geometry,Array	Easy
1267	Count Servers that Communicate	Graph,Array	Medium
1268	Search Suggestions System	String	Medium
1269	Number of Ways to Stay in the Same Place After Some Steps	Dynamic Programming	Hard
1270	All People Report to the Given Manager		Medium
1271	Hexspeak	Math,String	Easy
1272	Remove Interval	Math,Line Sweep	Medium
1273	Delete Tree Nodes	Depth-first Search,Dynamic Programming	Medium
1274	Number of Ships in a Rectangle	Divide and Conquer	Hard
1275	Find Winner on a Tic Tac Toe Game	Array	Easy
1276	Number of Burgers with No Waste of Ingredients	Greedy,Math	Medium
1277	Count Square Submatrices with All Ones	Array,Dynamic Programming	Medium
1278	Palindrome Partitioning III	Dynamic Programming	Hard
1279	Traffic Light Controlled Intersection		Easy
1280	Students and Examinations		Easy
1281	Subtract the Product and Sum of Digits of an Integer	Math	Easy
1282	Group the People Given the Group Size They Belong To	Greedy	Medium
1283	Find the Smallest Divisor Given a Threshold	Binary Search	Medium
1284	Minimum Number of Flips to Convert Binary Matrix to Zero Matrix	Breadth-first Search	Hard
1285	Find the Start and End Number of Continuous Ranges		Medium
1286	Iterator for Combination	Design,Backtracking	Medium
1287	Element Appearing More Than 25% In Sorted Array	Array	Easy
1288	Remove Covered Intervals	Line Sweep	Medium
1289	Minimum Falling Path Sum II	Dynamic Programming	Hard
1290	Convert Binary Number in a Linked List to Integer	Bit Manipulation,Linked List	Easy
1291	Sequential Digits	Backtracking	Medium
1292	Maximum Side Length of a Square with Sum Less than or Equal to Threshold	Array,Binary Search	Medium
1293	Shortest Path in a Grid with Obstacles Elimination	Breadth-first Search	Hard
1294	Weather Type in Each Country		Easy
1295	Find Numbers with Even Number of Digits	Array	Easy
1296	Divide Array in Sets of K Consecutive Numbers	Greedy,Array	Medium
1297	Maximum Number of Occurrences of a Substring	Bit Manipulation,String	Medium
1298	Maximum Candies You Can Get from Boxes	Breadth-first Search	Hard
1299	Replace Elements with Greatest Element on Right Side	Array	Easy
1300	Sum of Mutated Array Closest to Target	Array,Binary Search	Medium
1301	Number of Paths with Max Score	Dynamic Programming	Hard
1302	Deepest Leaves Sum	Tree,Depth-first Search	Medium
1303	Find the Team Size		Easy
1304	Find N Unique Integers Sum up to Zero	Array	Easy
1305	All Elements in Two Binary Search Trees	Sort,Tree	Medium
1306	Jump Game III	Breadth-first Search,Graph	Medium
1307	Verbal Arithmetic Puzzle	Math,Backtracking	Hard
1308	Running Total for Different Genders		Medium
1309	Decrypt String from Alphabet to Integer Mapping	String	Easy
1310	XOR Queries of a Subarray	Bit Manipulation	Medium
1311	Get Watched Videos by Your Friends	Breadth-first Search,Hash Table,String	Medium
1312	Minimum Insertion Steps to Make a String Palindrome	Dynamic Programming	Hard
1313	Decompress Run-Length Encoded List	Array	Easy
1314	Matrix Block Sum	Dynamic Programming	Medium
1315	Sum of Nodes with Even-Valued Grandparent	Tree,Depth-first Search	Medium
1316	Distinct Echo Substrings	String	Hard
1317	Convert Integer to the Sum of Two No-Zero Integers	Math	Easy
1318	Minimum Flips to Make a OR b Equal to c	Bit Manipulation	Medium
1319	Number of Operations to Make Network Connected	Depth-first Search,Breadth-first Search,Union Find	Medium
1320	Minimum Distance to Type a Word Using Two Fingers	Dynamic Programming	Hard
1321	Restaurant Growth		Medium
1322	Ads Performance		Easy
1323	Maximum 69 Number	Math	Easy
1324	Print Words Vertically	String	Medium
1325	Delete Leaves With a Given Value	Tree	Medium
1326	Minimum Number of Taps to Open to Water a Garden	Greedy,Dynamic Programming	Hard
1327	List the Products Ordered in a Period		Easy
1328	Break a Palindrome	String	Medium
1329	Sort the Matrix Diagonally	Sort,Array	Medium
1330	Reverse Subarray To Maximize Array Value	Array,Math	Hard
1331	Rank Transform of an Array	Array	Easy
1332	Remove Palindromic Subsequences	String	Easy
1333	Filter Restaurants by Vegan-Friendly, Price and Distance	Sort,Array	Medium
1334	Find the City With the Smallest Number of Neighbors at a Threshold Distance	Graph	Medium
1335	Minimum Difficulty of a Job Schedule	Dynamic Programming	Hard
1336	Number of Transactions per Visit		Hard
1337	The K Weakest Rows in a Matrix	Array,Binary Search	Easy
1338	Reduce Array Size to The Half	Greedy,Array	Medium
1339	Maximum Product of Splitted Binary Tree	Tree,Dynamic Programming	Medium
1340	Jump Game V	Dynamic Programming	Hard
1341	Movie Rating		Medium
1342	Number of Steps to Reduce a Number to Zero	Bit Manipulation	Easy
1343	Number of Sub-arrays of Size K and Average Greater than or Equal to Threshold	Array	Medium
1344	Angle Between Hands of a Clock	Math	Medium
1345	Jump Game IV	Breadth-first Search	Hard
1346	Check If N and Its Double Exist	Array	Easy
1347	Minimum Number of Steps to Make Two Strings Anagram	String	Medium
1348	Tweet Counts Per Frequency	Design	Medium
1349	Maximum Students Taking Exam	Dynamic Programming	Hard
1350	Students With Invalid Departments		Easy
1351	Count Negative Numbers in a Sorted Matrix	Array,Binary Search	Easy
1352	Product of the Last K Numbers	Design,Array	Medium
1353	Maximum Number of Events That Can Be Attended	Greedy,Sort,Segment Tree	Medium
1354	Construct Target Array With Multiple Sums	Greedy	Hard
1355	Activity Participants		Medium
1356	Sort Integers by The Number of 1 Bits	Sort,Bit Manipulation	Easy
1357	Apply Discount Every n Orders	Design	Medium
1358	Number of Substrings Containing All Three Characters	String	Medium
1359	Count All Valid Pickup and Delivery Options	Math,Dynamic Programming	Hard
1360	Number of Days Between Two Dates		Easy
1361	Validate Binary Tree Nodes	Graph	Medium
1362	Closest Divisors	Math	Medium
1363	Largest Multiple of Three	Math,Dynamic Programming	Hard
1364	Number of Trusted Contacts of a Customer		Medium
1365	How Many Numbers Are Smaller Than the Current Number	Array,Hash Table	Easy
1366	Rank Teams by Votes	Sort,Array	Medium
1367	Linked List in Binary Tree	Tree,Linked List,Dynamic Programming	Medium
1368	Minimum Cost to Make at Least One Valid Path in a Grid	Breadth-first Search	Hard
1369	Get the Second Most Recent Activity		Hard
1370	Increasing Decreasing String	Sort,String	Easy
1371	Find the Longest Substring Containing Vowels in Even Counts	String	Medium
1372	Longest ZigZag Path in a Binary Tree	Tree,Dynamic Programming	Medium
1373	Maximum Sum BST in Binary Tree	Binary Search Tree,Dynamic Programming	Hard
1374	Generate a String With Characters That Have Odd Counts	String	Easy
1375	Bulb Switcher III	Array	Medium
1376	Time Needed to Inform All Employees	Depth-first Search	Medium
1377	Frog Position After T Seconds	Depth-first Search	Hard
1378	Replace Employee ID With The Unique Identifier		Easy
1379	Find a Corresponding Node of a Binary Tree in a Clone of That Tree	Tree	Medium
1380	Lucky Numbers in a Matrix	Array	Easy
1381	Design a Stack With Increment Operation	Stack,Design	Medium
1382	Balance a Binary Search Tree	Binary Search Tree	Medium
1383	Maximum Performance of a Team	Greedy,Sort	Hard
1384	Total Sales Amount by Year		Hard
1385	Find the Distance Value Between Two Arrays	Array	Easy
1386	Cinema Seat Allocation	Greedy,Array	Medium
1387	Sort Integers by The Power Value	Sort,Graph	Medium
1388	Pizza With 3n Slices	Dynamic Programming	Hard
1389	Create Target Array in the Given Order	Array	Easy
1390	Four Divisors	Math	Medium
1391	Check if There is a Valid Path in a Grid	Depth-first Search,Breadth-first Search	Medium
1392	Longest Happy Prefix	String	Hard

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