Previous Questions

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ID	Questions
1	Two Sum
2	Add Two Numbers
3	Longest Substring Without Repeating Characters
4	Median of Two Sorted Arrays
5	Longest Palindromic Substring
6	Zigzag Conversion
7	Reverse Integer
8	String to Integer (atoi)
9	Palindrome Number
10	Regular Expression Matching
11	Container With Most Water
12	Integer to Roman
13	Roman to Integer
14	Longest Common Prefix
15	3Sum
16	3Sum Closest
17	Letter Combinations of a Phone Number
18	4Sum
19	Remove Nth Node From End of List
20	Valid Parentheses
21	Merge Two Sorted Lists
22	Generate Parentheses
23	Merge k Sorted Lists
24	Swap Nodes in Pairs
25	Reverse Nodes in k-Group
26	Remove Duplicates from Sorted Array
27	Remove Element
28	Find the Index of the First Occurrence in a String
29	Divide Two Integers
31	Next Permutation
32	Longest Valid Parentheses
33	Search in Rotated Sorted Array
34	Find First and Last Position of Element in Sorted Array
35	Search Insert Position
36	Valid Sudoku
37	Sudoku Solver
38	Count and Say
39	Combination Sum
40	Combination Sum II
41	First Missing Positive
42	Trapping Rain Water
43	Multiply Strings
44	Wildcard Matching
45	Jump Game II
46	Permutations
48	Rotate Image
49	Group Anagrams
50	Pow(x, n)
51	N-Queens
53	Maximum Subarray
54	Spiral Matrix
55	Jump Game
56	Merge Intervals
57	Insert Interval
58	Length of Last Word
59	Spiral Matrix II
61	Rotate List
62	Unique Paths
63	Unique Paths II
65	Valid Number
66	Plus One
67	Add Binary
68	Text Justification
69	Sqrt(x)
70	Climbing Stairs
71	Simplify Path
72	Edit Distance
73	Set Matrix Zeroes
74	Search a 2D Matrix
75	Sort Colors
76	Minimum Window Substring
77	Combinations
78	Subsets
79	Word Search
80	Remove Duplicates from Sorted Array II
81	Search in Rotated Sorted Array II
83	Remove Duplicates from Sorted List
84	Largest Rectangle in Histogram
85	Maximal Rectangle
86	Partition List
87	Scramble String
88	Merge Sorted Array
90	Subsets II
91	Decode Ways
92	Reverse Linked List II
93	Restore IP Addresses
94	Binary Tree Inorder Traversal
95	Unique Binary Search Trees II
98	Validate Binary Search Tree
101	Symmetric Tree
102	Binary Tree Level Order Traversal
103	Binary Tree Zigzag Level Order Traversal
104	Maximum Depth of Binary Tree
109	Convert Sorted List to Binary Search Tree
110	Balanced Binary Tree
111	Minimum Depth of Binary Tree
112	Path Sum
113	Path Sum II
114	Flatten Binary Tree to Linked List
116	Populating Next Right Pointers in Each Node
117	Populating Next Right Pointers in Each Node II
118	Pascal’s Triangle
121	Best Time to Buy and Sell Stock
122	Best Time to Buy and Sell Stock II
124	Binary Tree Maximum Path Sum
125	Valid Palindrome
126	Word Ladder II
127	Word Ladder
128	Longest Consecutive Sequence
129	Sum Root to Leaf Numbers
131	Palindrome Partitioning
133	Clone Graph
134	Gas Station
135	Candy
136	Single Number
138	Copy List with Random Pointer
139	Word Break
140	Word Break II
143	Reorder List
146	LRU Cache
148	Sort List
150	Evaluate Reverse Polish Notation
151	Reverse Words in a String
152	Maximum Product Subarray
153	Find Minimum in Rotated Sorted Array
155	Min Stack
157	Read N Characters Given Read4
158	Read N Characters Given read4 II - Call Multiple Times
159	Longest Substring with At Most Two Distinct Characters
160	Intersection of Two Linked Lists
161	One Edit Distance
162	Find Peak Element
163	Missing Ranges
164	Maximum Gap
166	Fraction to Recurring Decimal
167	Two Sum II - Input Array Is Sorted
168	Excel Sheet Column Title
169	Majority Element
171	Excel Sheet Column Number
173	Binary Search Tree Iterator
179	Largest Number
180	Consecutive Numbers
181	Employees Earning More Than Their Managers
184	Department Highest Salary
185	Department Top Three Salaries
189	Rotate Array
190	Reverse Bits
191	Number of 1 Bits
198	House Robber
199	Binary Tree Right Side View
200	Number of Islands
202	Happy Number
203	Remove Linked List Elements
206	Reverse Linked List
207	Course Schedule
208	Implement Trie (Prefix Tree)
209	Minimum Size Subarray Sum
210	Course Schedule II
211	Design Add and Search Words Data Structure
212	Word Search II
213	House Robber II
215	Kth Largest Element in an Array
217	Contains Duplicate
218	The Skyline Problem
219	Contains Duplicate II
221	Maximal Square
223	Rectangle Area
224	Basic Calculator
226	Invert Binary Tree
227	Basic Calculator II
229	Majority Element II
230	Kth Smallest Element in a BST
234	Palindrome Linked List
235	Lowest Common Ancestor of a Binary Search Tree
236	Lowest Common Ancestor of a Binary Tree
237	Delete Node in a Linked List
238	Product of Array Except Self
239	Sliding Window Maximum
240	Search a 2D Matrix II
241	Different Ways to Add Parentheses
242	Valid Anagram
243	Shortest Word Distance
246	Strobogrammatic Number
247	Strobogrammatic Number II
249	Group Shifted Strings
252	Meeting Rooms
253	Meeting Rooms II
257	Binary Tree Paths
259	3Sum Smaller
260	Single Number III
261	Graph Valid Tree
263	Ugly Number
265	Paint House II
266	Palindrome Permutation
267	Palindrome Permutation II
268	Missing Number
269	Alien Dictionary
270	Closest Binary Search Tree Value
271	Encode and Decode Strings
273	Integer to English Words
274	H-Index
275	H-Index II
277	Find the Celebrity
278	First Bad Version
282	Expression Add Operators
283	Move Zeroes
284	Peeking Iterator
285	Inorder Successor in BST
286	Walls and Gates
287	Find the Duplicate Number
290	Word Pattern
295	Find Median from Data Stream
296	Best Meeting Point
297	Serialize and Deserialize Binary Tree
298	Binary Tree Longest Consecutive Sequence
299	Bulls and Cows
300	Longest Increasing Subsequence
301	Remove Invalid Parentheses
303	Range Sum Query - Immutable
304	Range Sum Query 2D - Immutable
310	Minimum Height Trees
311	Sparse Matrix Multiplication
314	Binary Tree Vertical Order Traversal
317	Shortest Distance from All Buildings
319	Bulb Switcher
322	Coin Change
323	Number of Connected Components in an Undirected Graph
325	Maximum Size Subarray Sum Equals k
328	Odd Even Linked List
329	Longest Increasing Path in a Matrix
332	Reconstruct Itinerary
333	Largest BST Subtree
334	Increasing Triplet Subsequence
337	House Robber III
338	Counting Bits
339	Nested List Weight Sum
340	Longest Substring with At Most K Distinct Characters
341	Flatten Nested List Iterator
343	Integer Break
344	Reverse String
346	Moving Average from Data Stream
347	Top K Frequent Elements
348	Design Tic-Tac-Toe
349	Intersection of Two Arrays
350	Intersection of Two Arrays II
366	Find Leaves of Binary Tree
367	Valid Perfect Square
371	Sum of Two Integers
373	Find K Pairs with Smallest Sums
374	Guess Number Higher or Lower
377	Combination Sum IV
378	Kth Smallest Element in a Sorted Matrix
380	Insert Delete GetRandom O(1)
381	Insert Delete GetRandom O(1) - Duplicates allowed
383	Ransom Note
384	Shuffle an Array
386	Lexicographical Numbers
387	First Unique Character in a String
392	Is Subsequence
394	Decode String
398	Random Pick Index
399	Evaluate Division
402	Remove K Digits
404	Sum of Left Leaves
406	Queue Reconstruction by Height
408	Valid Word Abbreviation
410	Split Array Largest Sum
412	Fizz Buzz
415	Add Strings
416	Partition Equal Subset Sum
419	Battleships in a Board
424	Longest Repeating Character Replacement
435	Non-overlapping Intervals
437	Path Sum III
438	Find All Anagrams in a String
442	Find All Duplicates in an Array
443	String Compression
445	Add Two Numbers II
448	Find All Numbers Disappeared in an Array
450	Delete Node in a BST
451	Sort Characters By Frequency
452	Minimum Number of Arrows to Burst Balloons
460	LFU Cache
461	Hamming Distance
463	Island Perimeter
477	Total Hamming Distance
480	Sliding Window Median
490	The Maze
493	Reverse Pairs
494	Target Sum
496	Next Greater Element I
498	Diagonal Traverse
501	Find Mode in Binary Search Tree
503	Next Greater Element II
509	Inorder Successor in BST II
515	Find Largest Value in Each Tree Row
516	Longest Palindromic Subsequence
518	Coin Change II
523	Continuous Subarray Sum
525	Contiguous Array
528	Swapping Nodes in a Linked List
529	Minesweeper
530	Minimum Absolute Difference in BST
535	Encode and Decode TinyURL
536	Construct Binary Tree from String
538	Convert BST to Greater Tree
540	Single Element in a Sorted Array
542	01 Matrix
543	Diameter of Binary Tree
545	Boundary of Binary Tree
554	Brick Wall
556	Next Greater Element III
557	Reverse Words in a String III
560	Subarray Sum Equals K
567	Permutation in String
572	Subtree of Another Tree
578	Get Highest Answer Rate Question
583	Delete Operation for Two Strings
593	Valid Square
595	Big Countries
597	Friend Requests I: Overall Acceptance Rate
602	Friend Requests II: Who Has the Most Friends
605	Can Place Flowers
606	Construct String from Binary Tree
610	Triangle Judgement
611	Valid Triangle Number
616	Add Bold Tag in String
617	Merge Two Binary Trees
621	Task Scheduler
623	Add One Row to Tree
633	Sum of Square Numbers
636	Exclusive Time of Functions
637	Average of Levels in Binary Tree
639	Decode Ways II
642	Design Search Autocomplete System
643	Maximum Average Subarray I
647	Palindromic Substrings
649	Dota2 Senate
653	Two Sum IV - Input is a BST
658	Find K Closest Elements
661	Image Smoother
662	Maximum Width of Binary Tree
669	Trim a Binary Search Tree
670	Maximum Swap
673	Number of Longest Increasing Subsequence
674	Longest Continuous Increasing Subsequence
676	Implement Magic Dictionary
678	Valid Parenthesis String
680	Valid Palindrome II
684	Redundant Connection
687	Longest Univalue Path
689	Maximum Sum of 3 Non-Overlapping Subarrays
691	Stickers to Spell Word
692	Top K Frequent Words
695	Max Area of Island
698	Partition to K Equal Sum Subsets
711	Number of Distinct Islands II
713	Subarray Product Less Than K
714	Best Time to Buy and Sell Stock with Transaction Fee
716	Max Stack
721	Accounts Merge
723	Candy Crush
724	Find Pivot Index
733	Flood Fill
735	Asteroid Collision
739	Daily Temperatures
740	Delete and Earn
746	Prefix and Suffix Search
751	Number Of Corner Rectangles
753	Open the Lock
758	Convert Binary Search Tree to Sorted Doubly Linked List
766	Flatten a Multilevel Doubly Linked List
768	Partition Labels
769	Largest Plus Sign
777	Toeplitz Matrix
778	Reorganize String
785	Basic Calculator III
789	Kth Largest Element in a Stream
792	Binary Search
794	Swim in Rising Water
795	K-th Symbol in Grammar
800	Letter Case Permutation
801	Is Graph Bipartite?
803	Cheapest Flights Within K Stops
804	Rotated Digits
807	Custom Sort String
808	Number of Matching Subsequences
813	All Paths From Source to Target
817	Design HashMap
819	Minimum Swaps To Make Sequences Increasing
832	Binary Tree Pruning
850	Insert into a Sorted Circular Linked List
851	Goat Latin
852	Friends Of Appropriate Ages
854	Making A Large Island
860	Design Circular Queue
863	Sum of Distances in Tree
865	Robot Room Cleaner
866	Rectangle Overlap
877	Shortest Path Visiting All Nodes
882	Peak Index in a Mountain Array
886	Score of Parentheses
889	Buddy Strings
893	All Nodes Distance K in Binary Tree
896	Smallest Subtree with all the Deepest Nodes
907	Koko Eating Bananas
908	Middle of the Linked List
912	Random Pick with Weight
929	Groups of Special-Equivalent Strings
930	All Possible Full Binary Trees
931	Maximum Frequency Stack
932	Monotonic Array
933	Increasing Order Search Tree
937	Online Stock Span
941	Sort Array By Parity
948	Sort an Array
955	Complete Binary Tree Inserter
957	Minimum Add to Make Parentheses Valid
971	Shortest Bridge
972	Knight Dialer
975	Range Sum of BST
976	Minimum Area Rectangle
978	Valid Mountain Array
990	Verifying an Alien Dictionary
998	Check Completeness of a Binary Tree
1008	Binary Tree Cameras
1014	K Closest Points to Origin
1016	Subarray Sums Divisible by K
1019	Squares of a Sorted Array
1025	Minimum Cost For Tickets
1028	Interval List Intersections
1029	Vertical Order Traversal of a Binary Tree
1031	Add to Array-Form of Integer
1035	Cousins in Binary Tree
1038	Number of Squareful Arrays
1040	Maximum Binary Tree II
1046	Max Consecutive Ones III
1050	Construct Binary Search Tree from Preorder Traversal
1051	Shortest Way to Form String
1056	Capacity To Ship Packages Within D Days
1059	Missing Element in Sorted Array
1073	Number of Enclaves
1078	Remove Outermost Parentheses
1091	Maximum Average Subtree
1092	Maximum Difference Between Node and Ancestor
1095	Two City Scheduling
1099	Path With Maximum Minimum Value
1103	Moving Stones Until Consecutive
1113	Moving Stones Until Consecutive II
1114	Binary Search Tree to Greater Sum Tree
1116	Maximum Level Sum of a Binary Tree
1121	Partition Array for Maximum Sum
1128	Remove All Adjacent Duplicates In String
1139	Previous Permutation With One Swap
1142	Minimum Knight Moves
1149	Intersection of Three Sorted Arrays
1161	Project Employees I
1162	Project Employees II
1163	Project Employees III
1171	Shortest Path in Binary Matrix
1176	Design A Leaderboard
1177	Tree Diameter
1178	Valid Palindrome III
1184	Car Pooling
1185	Find in Mountain Array
1205	Defanging an IP Address
1207	Delete Nodes And Return Forest
1215	Reported Posts
1218	Lowest Common Ancestor of Deepest Leaves
1221	Element Appearing More Than 25% In Sorted Array
1222	Remove Covered Intervals
1231	Replace Elements with Greatest Element on Right Side
1237	Reported Posts II
1245	User Activity for the Past 30 Days I
1246	User Activity for the Past 30 Days II
1256	Rank Transform of an Array
1271	Web Crawler
1275	Validate Binary Tree Nodes
1285	Balance a Binary Search Tree
1288	Maximum Subarray Sum with One Deletion
1296	Kth Ancestor of a Tree Node
1300	Critical Connections in a Network
1305	Number of Visible People in a Queue
1319	Unique Number of Occurrences
1320	Remove All Adjacent Duplicates in String II
1337	Design Skiplist
1338	Queries Quality and Percentage
1357	Report Contiguous Dates
1366	First Unique Number
1368	Web Crawler Multithreaded
1371	Minimum Remove to Make Valid Parentheses
1374	Leftmost Column with at Least a One
1377	Number of Comments per Post
1382	Calculate Amount Paid in Taxes
1397	Search Suggestions System
1399	Page Recommendations
1400	Find Winner on a Tic Tac Toe Game
1404	Print Immutable Linked List in Reverse
1406	Subtract the Product and Sum of Digits of an Integer
1414	Shortest Path in a Grid with Obstacles Elimination
1427	All Elements in Two Binary Search Trees
1446	Angle Between Hands of a Clock
1453	Ads Performance
1459	Apply Discount Every n Orders
1460	Number of Substrings Containing All Three Characters
1466	Jump Game V
1498	Find a Corresponding Node of a Binary Tree in a Clone of That Tree
1516	The k-th Lexicographical String of All Happy Strings of Length n
1536	Customers Who Bought Products A and B but Not C
1539	Diagonal Traverse II
1542	Consecutive Characters
1550	Find the Kth Smallest Sum of a Matrix With Sorted Rows
1554	Minimum Time to Collect All Apples in a Tree
1556	Make Two Arrays Equal by Reversing Subarrays
1563	Maximum Number of Darts Inside of a Circular Dartboard
1578	Apples & Oranges
1579	Active Users
1585	The kth Factor of n
1603	Running Sum of 1d Array
1621	Number of Subsequences That Satisfy the Given Sum Condition
1635	Number of Good Pairs
1646	Kth Missing Positive Number
1648	Minimum Insertions to Balance a Parentheses String
1663	Detect Cycles in 2D Grid
1665	Diameter of N-Ary Tree
1693	Sum of All Odd Length Subarrays
1706	Min Cost to Connect All Points
1713	Dot Product of Two Sparse Vectors
1729	Binary Search Tree Iterator II
1737	Maximum Nesting Depth of the Parentheses
1760	Check Array Formation Through Concatenation
1777	Determine if Two Strings Are Close
1780	Lowest Common Ancestor of a Binary Tree II
1781	Check If Two String Arrays are Equivalent
1782	Smallest String With A Given Numeric Value
1790	Lowest Common Ancestor of a Binary Tree III
1801	Average Time of Process per Machine
1819	Construct the Lexicographically Largest Valid Sequence
1842	Number of Calls Between Two Persons
1848	Sum of Unique Elements
1883	Find Distance in a Binary Tree
1894	Merge Strings Alternately
1899	Count Items Matching a Rule
1908	Recyclable and Low Fat Products
1909	Buildings With an Ocean View
1915	Check if One String Swap Can Make Strings Equal
1931	Shortest Path in a Hidden Grid
1942	Primary Department for Each Employee
1951	Find the Winner of the Circular Game
1959	Minimum Path Cost in a Hidden Grid
1960	Check if the Sentence Is Pangram
1962	Single-Threaded CPU
1970	Sorting the Sentence
1980	Faulty Sensor
1995	Finding Pairs With a Certain Sum
2019	Product of Two Run-Length Encoded Arrays
2020	Remove One Element to Make the Array Strictly Increasing
2038	Nearest Exit from Entrance in Maze
2040	Minimum Cost to Reach Destination in Time
2045	Cutting Ribbons
2046	Page Recommendations II
2048	Build Array from Permutation
2078	Maximum Compatibility Score Sum
2090	Number of Ways to Arrive at Destination
2095	Minimum Number of Swaps to Make the String Balanced
2097	Strong Friendship
2102	Find the Middle Index in Array
2107	Find Unique Binary String
2123	The Number of Weak Characters in the Game
2126	Count Nodes Equal to Sum of Descendants
2133	Number of Pairs of Strings With Concatenation Equal to Target
2134	Maximize the Confusion of an Exam
2140	Longest Subsequence Repeated k Times
2160	Minimum Operations to Make a Uni-Value Grid
2184	Check if an Original String Exists Given Two Encoded Strings
2211	K Radius Subarray Averages
2217	Step-By-Step Directions From a Binary Tree Node to Another
2316	Count Hills and Valleys in an Array
2335	Finding the Topic of Each Post
2342	Minimum Average Difference
2347	Count Nodes Equal to Average of Subtree
2374	Steps to Make Array Non-decreasing
2383	Add Two Integers
2473	Max Sum of a Pair With Equal Sum of Digits
2483	Task Scheduler II
2550	Words Within Two Edits of Dictionary
2639	Separate the Digits in an Array
2662	Check Knight Tour Configuration
2696	The Number of Beautiful Subsets
2732	Counter
2809	Create Hello World Function
2917	Count Pairs Whose Sum is Less than Target
3206	Find Common Elements Between Two Arrays