Sorted by frequency of problems that appear in real interviews.
Last updated: October 2, 2017
Google (214)
534 Design TinyURL
388 Longest Absolute File Path
683 K Empty Slots
340 Longest Substring with At Most K Distinct Characters
681 Next Closest Time
482 License Key Formatting
308 Range Sum Query 2D – Mutable
298 Binary Tree Longest Consecutive Sequence
346 Moving Average from Data Stream
418 Sentence Screen Fitting
281 Zigzag Iterator
425 Word Squares
361 Bomb Enemy
394 Decode String
393 UTF-8 Validation
163 Missing Ranges
66 Plus One
568 Maximum Vacation Days
317 Shortest Distance from All Buildings
351 Android Unlock Patterns
271 Encode and Decode Strings
288 Unique Word Abbreviation
289 Game of Life
200 Number of Islands
305 Number of Islands II
259 3Sum Smaller
280 Wiggle Sort
246 Strobogrammatic Number
417 Pacific Atlantic Water Flow
218 The Skyline Problem
279 Perfect Squares
406 Queue Reconstruction by Height
329 Longest Increasing Path in a Matrix
159 Longest Substring with At Most Two Distinct Characters
345 Reverse Vowels of a String
56 Merge Intervals
247 Strobogrammatic Number II
524 Longest Word in Dictionary through Deleting
399 Evaluate Division
284 Peeking Iterator
391 Perfect Rectangle
407 Trapping Rain Water II
286 Walls and Gates
228 Summary Ranges
297 Serialize and Deserialize Binary Tree
294 Flip Game II
146 LRU Cache
471 Encode String with Shortest Length
362 Design Hit Counter
463 Island Perimeter
616 Add Bold Tag in String
380 Insert Delete GetRandom O(1)
320 Generalized Abbreviation
401 Binary Watch
295 Find Median from Data Stream
42 Trapping Rain Water
249 Group Shifted Strings
341 Flatten Nested List Iterator
276 Paint Fence
360 Sort Transformed Array
411 Minimum Unique Word Abbreviation
315 Count of Smaller Numbers After Self
465 Optimal Account Balancing
266 Palindrome Permutation
253 Meeting Rooms II
269 Alien Dictionary
389 Find the Difference
239 Sliding Window Maximum
128 Longest Consecutive Sequence
679 24 Game
274 H-Index
293 Flip Game
20 Valid Parentheses
359 Logger Rate Limiter
505 The Maze II
490 The Maze
139 Word Break
270 Closest Binary Search Tree Value
162 Find Peak Element
318 Maximum Product of Word Lengths
212 Word Search II
230 Kth Smallest Element in a BST
158 Read N Characters Given Read4 II – Call multiple times
684 Redundant Connection
415 Add Strings
369 Plus One Linked List
400 Nth Digit
587 Erect the Fence
422 Valid Word Square
240 Search a 2D Matrix II
10 Regular Expression Matching
358 Rearrange String k Distance Apart
23 Merge k Sorted Lists
498 Diagonal Traverse
251 Flatten 2D Vector
332 Reconstruct Itinerary
373 Find K Pairs with Smallest Sums
4 Median of Two Sorted Arrays
155 Min Stack
140 Word Break II
484 Find Permutation
173 Binary Search Tree Iterator
17 Letter Combinations of a Phone Number
324 Wiggle Sort II
409 Longest Palindrome
31 Next Permutation
54 Spiral Matrix
327 Count of Range Sum
22 Generate Parentheses
336 Palindrome Pairs
57 Insert Interval
166 Fraction to Recurring Decimal
133 Clone Graph
460 LFU Cache
224 Basic Calculator
44 Wildcard Matching
231 Power of Two
363 Max Sum of Rectangle No Larger Than K
354 Russian Doll Envelopes
421 Maximum XOR of Two Numbers in an Array
50 Pow(x, n)
348 Design Tic-Tac-Toe
444 Sequence Reconstruction
503 Next Greater Element II
208 Implement Trie (Prefix Tree)
501 Find Mode in Binary Search Tree
309 Best Time to Buy and Sell Stock with Cooldown
402 Remove K Digits
382 Linked List Random Node
475 Heaters
551 Student Attendance Record I
272 Closest Binary Search Tree Value II
377 Combination Sum IV
214 Shortest Palindrome
302 Smallest Rectangle Enclosing Black Pixels
379 Design Phone Directory
353 Design Snake Game
459 Repeated Substring Pattern
542 01 Matrix
375 Guess Number Higher or Lower II
486 Predict the Winner
543 Diameter of Binary Tree
356 Line Reflection
397 Integer Replacement
282 Expression Add Operators
408 Valid Word Abbreviation
321 Create Maximum Number
368 Largest Divisible Subset
530 Minimum Absolute Difference in BST
313 Super Ugly Number
331 Verify Preorder Serialization of a Binary Tree
323 Number of Connected Components in an Undirected Graph
261 Graph Valid Tree
451 Sort Characters By Frequency
374 Guess Number Higher or Lower
378 Kth Smallest Element in a Sorted Matrix
448 Find All Numbers Disappeared in an Array
310 Minimum Height Trees
326 Power of Three
257 Binary Tree Paths
370 Range Addition
643 Maximum Average Subarray I
485 Max Consecutive Ones
638 Shopping Offers
483 Smallest Good Base
686 Repeated String Match
481 Magical String
480 Sliding Window Median
604 Design Compressed String Iterator
474 Ones and Zeroes 38
357 Count Numbers with Unique Digits
685 Redundant Connection II
469 Convex Polygon
583 Delete Operation for Two Strings
581 Shortest Unsorted Continuous Subarray
569 Median Employee Salary
689 Maximum Sum of 3 Non-Overlapping Subarrays
562 Longest Line of Consecutive One in Matrix
560 Subarray Sum Equals K
447 Number of Boomerangs
552 Student Attendance Record II
676 Implement Magic Dictionary
549 Binary Tree Longest Consecutive Sequence II
330 Patching Array
545 Boundary of Binary Tree
544 Output Contest Matches
668 Kth Smallest Number in Multiplication Table
667 Beautiful Arrangement II
541 Reverse String II
535 Encode and Decode TinyURL
665 Non-decreasing Array
533 Lonely Pixel II
531 Lonely Pixel I
316 Remove Duplicate Letters
659 Split Array into Consecutive Subsequences
314 Binary Tree Vertical Order Traversal
527 Word Abbreviation
312 Burst Balloons
526 Beautiful Arrangement
658 Find K Closest Elements
522 Longest Uncommon Subsequence II
521 Longest Uncommon Subsequence I
520 Detect Capital
514 Freedom Trail
506 Relative Ranks
657 Judge Route Circle
656 Coin Path
652 Find Duplicate Subtrees
651 4 Keys Keyboard
494 Target Sum
493 Reverse Pairs
644 Maximum Average Subarray II
487 Max Consecutive Ones II
687 Longest Univalue Path
Facebook (111)
534 Design TinyURL
283 Move Zeroes
301 Remove Invalid Parentheses
273 Integer to English Words
325 Maximum Size Subarray Sum Equals k
67 Add Binary
621 Task Scheduler
253 Meeting Rooms II
17 Letter Combinations of a Phone Number
311 Sparse Matrix Multiplication
91 Decode Ways 19.8%
297 Serialize and Deserialize Binary Tree
314 Binary Tree Vertical Order Traversal
10 Regular Expression Matching
15 3Sum
158 Read N Characters Given Read4 II – Call multiple times
278 First Bad Version
277 Find the Celebrity
200 Number of Islands
76 Minimum Window Substring
257 Binary Tree Paths
282 Expression Add Operators
23 Merge k Sorted Lists
157 Read N Characters Given Read4
121 Best Time to Buy and Sell Stock
602 Friend Requests II: Who Has the Most Friends
56 Merge Intervals
161 One Edit Distance
173 Binary Search Tree Iterator
1 Two Sum
543 Diameter of Binary Tree
211 Add and Search Word – Data structure design
341 Flatten Nested List Iterator
252 Meeting Rooms
125 Valid Palindrome
597 Friend Requests I: Overall Acceptance Rate
139 Word Break
636 Exclusive Time of Functions
285 Inorder Successor in BST
78 Subsets
98 Validate Binary Search Tree
43 Multiply Strings
75 Sort Colors
670 Maximum Swap
57 Insert Interval
133 Clone Graph
215 Kth Largest Element in an Array
33 Search in Rotated Sorted Array
13 Roman to Integer
206 Reverse Linked List
79 Word Search
494 Target Sum
236 Lowest Common Ancestor of a Binary Tree
398 Random Pick Index
477 Total Hamming Distance
38 Count and Say
680 Valid Palindrome II
49 Group Anagrams
88 Merge Sorted Array
218 The Skyline Problem
146 LRU Cache
238 Product of Array Except Self
209 Minimum Size Subarray Sum
102 Binary Tree Level Order Traversal
90 Subsets II
71 Simplify Path
286 Walls and Gates
128 Longest Consecutive Sequence
639 Decode Ways II
523 Continuous Subarray Sum
334 Increasing Triplet Subsequence
208 Implement Trie (Prefix Tree)
28 Implement strStr()
269 Alien Dictionary
127 Word Ladder
647 Palindromic Substrings
377 Combination Sum IV
20 Valid Parentheses
44 Wildcard Matching
554 Brick Wall
235 Lowest Common Ancestor of a Binary Search Tree
380 Insert Delete GetRandom O(1)
50 Pow(x, n)
117 Populating Next Right Pointers in Each Node II
69 Sqrt(x)
461 Hamming Distance
85 Maximal Rectangle
210 Course Schedule II
26 Remove Duplicates from Sorted Array
68 Text Justification
221 Maximal Square
274 H-Index
404 Sum of Left Leaves
25 Reverse Nodes in k-Group
234 Palindrome Linked List
689 Maximum Sum of 3 Non-Overlapping Subarrays
80 Remove Duplicates from Sorted Array II
168 Excel Sheet Column Title
261 Graph Valid Tree
265 Paint House II
275 H-Index II
410 Split Array Largest Sum
525 Contiguous Array
674 Longest Continuous Increasing Subsequence
572 Subtree of Another Tree
578 Get Highest Answer Rate Question
637 Average of Levels in Binary Tree
642 Design Search Autocomplete System
653 Two Sum IV – Input is a BST
673 Number of Longest Increasing Subsequence
535 Encode and Decode TinyURL
Microsoft (92)
138 Copy List with Random Pointer
348 Design Tic-Tac-Toe
206 Reverse Linked List
419 Battleships in a Board
273 Integer to English Words
171 Excel Sheet Column Number
54 Spiral Matrix
88 Merge Sorted Array
445 Add Two Numbers II
236 Lowest Common Ancestor of a Binary Tree
200 Number of Islands
53 Maximum Subarray
1 Two Sum
235 Lowest Common Ancestor of a Binary Search Tree
186 Reverse Words in a String II
218 The Skyline Problem
21 Merge Two Sorted Lists
116 Populating Next Right Pointers in Each Node
103 Binary Tree Zigzag Level Order Traversal
297 Serialize and Deserialize Binary Tree
238 Product of Array Except Self
121 Best Time to Buy and Sell Stock
268 Missing Number
48 Rotate Image
75 Sort Colors
151 Reverse Words in a String
13 Roman to Integer
73 Set Matrix Zeroes
117 Populating Next Right Pointers in Each Node II
20 Valid Parentheses
141 Linked List Cycle
2 Add Two Numbers
33 Search in Rotated Sorted Array
168 Excel Sheet Column Title
24 Swap Nodes in Pairs
8 String to Integer (atoi)
237 Delete Node in a Linked List
146 LRU Cache
232 Implement Queue using Stacks
173 Binary Search Tree Iterator
98 Validate Binary Search Tree
208 Implement Trie (Prefix Tree)
174 Dungeon Game
212 Word Search II
4 Median of Two Sorted Arrays
5 Longest Palindromic Substring
285 Inorder Successor in BST
153 Find Minimum in Rotated Sorted Array
26 Remove Duplicates from Sorted Array
160 Intersection of Two Linked Lists
106 Construct Binary Tree from Inorder and Postorder Traversal
102 Binary Tree Level Order Traversal
23 Merge k Sorted Lists
25 Reverse Nodes in k-Group
215 Kth Largest Element in an Array
189 Rotate Array
191 Number of 1 Bits
567 Permutation in String
71 Simplify Path
387 First Unique Character in a String
15 3Sum
204 Count Primes
56 Merge Intervals
94 Binary Tree Inorder Traversal
165 Compare Version Numbers
28 Implement strStr()
46 Permutations
300 Longest Increasing Subsequence
91 Decode Ways
101 Symmetric Tree
270 Closest Binary Search Tree Value
114 Flatten Binary Tree to Linked List
79 Word Search
258 Add Digits
125 Valid Palindrome
124 Binary Tree Maximum Path Sum
162 Find Peak Element
112 Path Sum
654 Maximum Binary Tree
333 Largest BST Subtree
365 Water and Jug Problem
452 Minimum Number of Arrows to Burst Balloons
47 Permutations II
513 Find Bottom Left Tree Value
213 House Robber II
55 Jump Game
591 Tag Validator
631 Design Excel Sum Formula
642 Design Search Autocomplete System
650 2 Keys Keyboard
651 4 Keys Keyboard
672 Bulb Switcher II
Amazon (88)
534 Design TinyURL
675 Cut Off Trees for Golf Event
1 Two Sum
20 Valid Parentheses
146 LRU Cache
438 Find All Anagrams in a String
200 Number of Islands
48 Rotate Image
297 Serialize and Deserialize Binary Tree
138 Copy List with Random Pointer
236 Lowest Common Ancestor of a Binary Tree
460 LFU Cache
387 First Unique Character in a String
121 Best Time to Buy and Sell Stock
239 Sliding Window Maximum
5 Longest Palindromic Substring
17 Letter Combinations of a Phone Number
238 Product of Array Except Self
42 Trapping Rain Water
682 Baseball Game
127 Word Ladder
380 Insert Delete GetRandom O(1)
235 Lowest Common Ancestor of a Binary Search Tree
206 Reverse Linked List
23 Merge k Sorted Lists
155 Min Stack
2 Add Two Numbers
98 Validate Binary Search Tree
449 Serialize and Deserialize BST
240 Search a 2D Matrix II
234 Palindrome Linked List
517 Super Washing Machines
215 Kth Largest Element in an Array
139 Word Break
21 Merge Two Sorted Lists
49 Group Anagrams
126 Word Ladder II
3 Longest Substring Without Repeating Characters
242 Valid Anagram
529 Minesweeper
160 Intersection of Two Linked Lists
141 Linked List Cycle
186 Reverse Words in a String II
167 Two Sum II – Input array is sorted
15 3Sum
78 Subsets
535 Encode and Decode TinyURL
73 Set Matrix Zeroes
102 Binary Tree Level Order Traversal
508 Most Frequent Subtree Sum
8 String to Integer (atoi)
538 Convert BST to Greater Tree
204 Count Primes
199 Binary Tree Right Side View
414 Third Maximum Number
89 Gray Code
451 Sort Characters By Frequency
355 Design Twitter 2
119 Pascal’s Triangle II
662 Maximum Width of Binary Tree
645 Set Mismatch
617 Merge Two Binary Trees
661 Image Smoother
396 Rotate Function
646 Maximum Length of Pair Chain
545 Boundary of Binary Tree
606 Construct String from Binary Tree
640 Solve the Equation
663 Equal Tree Partition
459 Repeated Substring Pattern
516 Longest Palindromic Subsequence
532 K-diff Pairs in an Array
579 Find Cumulative Salary of an Employee
536 Construct Binary Tree from String
537 Complex Number Multiplication
553 Optimal Division
Bloomberg (66)
445 Add Two Numbers II
121 Best Time to Buy and Sell Stock
138 Copy List with Random Pointer
582 Kill Process
1 Two Sum
283 Move Zeroes
387 First Unique Character in a String
155 Min Stack
20 Valid Parentheses
146 LRU Cache
117 Populating Next Right Pointers in Each Node II
206 Reverse Linked List
50 Pow(x, n)
56 Merge Intervals
62 Unique Paths
42 Trapping Rain Water
69 Sqrt(x)
160 Intersection of Two Linked Lists
122 Best Time to Buy and Sell Stock II
2 Add Two Numbers
268 Missing Number
53 Maximum Subarray
98 Validate Binary Search Tree
287 Find the Duplicate Number
7 Reverse Integer
49 Group Anagrams
232 Implement Queue using Stacks
386 Lexicographical Numbers
151 Reverse Words in a String
215 Kth Largest Element in an Array
88 Merge Sorted Array
103 Binary Tree Zigzag Level Order Traversal
3 Longest Substring Without Repeating Characters
102 Binary Tree Level Order Traversal
208 Implement Trie (Prefix Tree)
139 Word Break
225 Implement Stack using Queues
105 Construct Binary Tree from Preorder and Inorder Traversal
230 Kth Smallest Element in a BST
141 Linked List Cycle
13 Roman to Integer
26 Remove Duplicates from Sorted Array
5 Longest Palindromic Substring
63 Unique Paths II 3
8 String to Integer (atoi)
297 Serialize and Deserialize Binary Tree
101 Symmetric Tree
172 Factorial Trailing Zeroes
79 Word Search
33 Search in Rotated Sorted Array
100 Same Tree
189 Rotate Array
15 3Sum
158 Read N Characters Given Read4 II – Call multiple times
24 Swap Nodes in Pairs
570 Managers with at Least 5 Direct Reports
16 3Sum Closest
131 Palindrome Partitioning
266 Palindrome Permutation
11 Container With Most Water
547 Friend Circles
556 Next Greater Element III
113 Path Sum II
110 Balanced Binary Tree
274 H-Index
669 Trim a Binary Search Tree
Uber (52)
380 Insert Delete GetRandom O(1)
262 Trips and Users
291 Word Pattern II
254 Factor Combinations
36 Valid Sudoku
297 Serialize and Deserialize Binary Tree
432 All O`one Data Structure
139 Word Break
146 LRU Cache
249 Group Shifted Strings
22 Generate Parentheses
535 Encode and Decode TinyURL
17 Letter Combinations of a Phone Number
54 Spiral Matrix
133 Clone Graph 2
49 Group Anagrams
450 Delete Node in a BST
290 Word Pattern
13 Roman to Integer
186 Reverse Words in a String II
208 Implement Trie (Prefix Tree)
10 Regular Expression Matching
37 Sudoku Solver
138 Copy List with Random Pointer
23 Merge k Sorted Lists
39 Combination Sum
140 Word Break II
230 Kth Smallest Element in a BST
207 Course Schedule
91 Decode Ways
1 Two Sum
337 House Robber III
33 Search in Rotated Sorted Array
161 One Edit Distance
242 Valid Anagram
78 Subsets
76 Minimum Window Substring
24 Swap Nodes in Pairs
202 Happy Number
121 Best Time to Buy and Sell Stock
206 Reverse Linked List
125 Valid Palindrome
104 Maximum Depth of Binary Tree
534 Design TinyURL
516 Longest Palindromic Subsequence
373 Find K Pairs with Smallest Sums
266 Palindrome Permutation
171 Excel Sheet Column Number
690 Employee Importance
648 Replace Words
8 String to Integer (atoi)
155 Min Stack
LinkedIn (48)
339 Nested List Weight Sum
244 Shortest Word Distance II
364 Nested List Weight Sum II
170 Two Sum III – Data structure design
256 Paint House
156 Binary Tree Upside Down
243 Shortest Word Distance
254 Factor Combinations
245 Shortest Word Distance III
366 Find Leaves of Binary Tree
205 Isomorphic Strings
297 Serialize and Deserialize Binary Tree
53 Maximum Subarray
605 Can Place Flowers
65 Valid Number
50 Pow(x, n)
149 Max Points on a Line
68 Text Justification
277 Find the Celebrity
56 Merge Intervals
187 Repeated DNA Sequences
311 Sparse Matrix Multiplication
236 Lowest Common Ancestor of a Binary Tree
102 Binary Tree Level Order Traversal
34 Search for a Range
464 Can I Win
1 Two Sum
152 Maximum Product Subarray
150 Evaluate Reverse Polish Notation
33 Search in Rotated Sorted Array
46 Permutations
76 Minimum Window Substring
238 Product of Array Except Self
104 Maximum Depth of Binary Tree
127 Word Ladder
101 Symmetric Tree
57 Insert Interval
103 Binary Tree Zigzag Level Order Traversal
198 House Robber
23 Merge k Sorted Lists
21 Merge Two Sorted Lists
47 Permutations II
173 Binary Search Tree Iterator
633 Sum of Square Numbers
367 Valid Perfect Square
515 Find Largest Value in Each Tree Row
671 Second Minimum Node In a Binary Tree
647 Palindromic Substrings
Twitter (34)
433 Minimum Genetic Mutation
608 Tree Node
585 Investments in 2016
296 Best Meeting Point
586 Customer Placing the Largest Number of Orders
468 Validate IP Address
580 Count Student Number in Departments
341 Flatten Nested List Iterator
269 Alien Dictionary
355 Design Twitter
251 Flatten 2D Vector
12 Integer to Roman
218 The Skyline Problem
161 One Edit Distance
146 LRU Cache
202 Happy Number
140 Word Break II
149 Max Points on a Line
208 Implement Trie (Prefix Tree)
60 Permutation Sequence
20 Valid Parentheses
42 Trapping Rain Water
10 Regular Expression Matching
235 Lowest Common Ancestor of a Binary Search Tree
56 Merge Intervals
206 Reverse Linked List
23 Merge k Sorted Lists
43 Multiply Strings
44 Wildcard Matching
118 Pascal’s Triangle
380 Insert Delete GetRandom O(1)
378 Kth Smallest Element in a Sorted Matrix
323 Number of Connected Components in an Undirected Graph
407 Trapping Rain Water II
Apple (29)
238 Product of Array Except Self
1 Two Sum
42 Trapping Rain Water
206 Reverse Linked List
191 Number of 1 Bits
237 Delete Node in a Linked List
284 Peeking Iterator
240 Search a 2D Matrix II
48 Rotate Image
149 Max Points on a Line
102 Binary Tree Level Order Traversal
236 Lowest Common Ancestor of a Binary Tree
70 Climbing Stairs
36 Valid Sudoku
215 Kth Largest Element in an Array
4 Median of Two Sorted Arrays
104 Maximum Depth of Binary Tree
28 Implement strStr()
190 Reverse Bits
7 Reverse Integer
221 Maximal Square
165 Compare Version Numbers
151 Reverse Words in a String
207 Course Schedule
257 Binary Tree Paths
69 Sqrt(x)
21 Merge Two Sorted Lists
118 Pascal’s Triangle
383 Ransom Note
Snapchat (26)
36 Valid Sudoku
289 Game of Life
253 Meeting Rooms II
269 Alien Dictionary
403 Frog Jump
37 Sudoku Solver
314 Binary Tree Vertical Order Traversal
127 Word Ladder
146 LRU Cache
140 Word Break II
161 One Edit Distance
377 Combination Sum IV
96 Unique Binary Search Trees
206 Reverse Linked List
39 Combination Sum
76 Minimum Window Substring
155 Min Stack
44 Wildcard Matching
151 Reverse Words in a String
402 Remove K Digits
270 Closest Binary Search Tree Value
527 Word Abbreviation
40 Combination Sum II
312 Burst Balloons
439 Ternary Expression Parser
635 Design Log Storage System
Airbnb (23)
336 Palindrome Pairs
251 Flatten 2D Vector
269 Alien Dictionary
68 Text Justification
1 Two Sum
198 House Robber
212 Word Search II
219 Contains Duplicate II
10 Regular Expression Matching
202 Happy Number
108 Convert Sorted Array to Binary Search Tree
136 Single Number
2 Add Two Numbers
160 Intersection of Two Linked Lists
217 Contains Duplicate
190 Reverse Bits
20 Valid Parentheses
220 Contains Duplicate III
385 Mini Parser
221 Maximal Square
23 Merge k Sorted Lists
227 Basic Calculator II
415 Add Strings
Zenefits (21)
42 Trapping Rain Water
52 N-Queens II
255 Verify Preorder Sequence in Binary Search Tree
317 Shortest Distance from All Buildings
251 Flatten 2D Vector
210 Course Schedule II
206 Reverse Linked List
109 Convert Sorted List to Binary Search Tree
200 Number of Islands
20 Valid Parentheses
146 LRU Cache
168 Excel Sheet Column Title
155 Min Stack
4 Median of Two Sorted Arrays
125 Valid Palindrome
207 Course Schedule
239 Sliding Window Maximum
229 Majority Element II
22 Generate Parentheses
261 Graph Valid Tree
169 Majority Element
Yelp (17)
599 Minimum Index Sum of Two Lists
56 Merge Intervals
564 Find the Closest Palindrome
347 Top K Frequent Elements
49 Group Anagrams
218 The Skyline Problem
14 Longest Common Prefix
127 Word Ladder
207 Course Schedule
1 Two Sum
3 Longest Substring Without Repeating Characters
380 Insert Delete GetRandom O(1)
206 Reverse Linked List
126 Word Ladder II
242 Valid Anagram
151 Reverse Words in a String
381 Insert Delete GetRandom O(1) – Duplicates allowed
Yahoo (14)
1 Two Sum
479 Largest Palindrome Product
13 Roman to Integer
217 Contains Duplicate
297 Serialize and Deserialize Binary Tree
146 LRU Cache
139 Word Break
4 Median of Two Sorted Arrays
284 Peeking Iterator
206 Reverse Linked List
141 Linked List Cycle
104 Maximum Depth of Binary Tree
491 Increasing Subsequences
624 Maximum Distance in Arrays
Pocket Gems (13)
347 Top K Frequent Elements
75 Sort Colors
28 Implement strStr()
285 Inorder Successor in BST
269 Alien Dictionary
133 Clone Graph
214 Shortest Palindrome
215 Kth Largest Element in an Array
139 Word Break
380 Insert Delete GetRandom O(1)
442 Find All Duplicates in an Array
424 Longest Repeating Character Replacement
600 Non-negative Integers without Consecutive Ones
Adobe (12)
1 Two Sum
195 Tenth Line
2 Add Two Numbers
292 Nim Game
237 Delete Node in a Linked List
4 Median of Two Sorted Arrays
3 Longest Substring Without Repeating Characters
206 Reverse Linked List
258 Add Digits
15 3Sum
169 Majority Element
70 Climbing Stairs
Leetcode problems classified by company 