Here are top 250 problems:
ID Title
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 Implement strStr() @@
29 Divide Two Integers @@
30 Substring with Concatenation of All Words @
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 @@
47 Permutations II @@
48 Rotate Image @@
49 Group Anagrams @@@@
50 Pow(x, n) @@
51 N-Queens @@
52 N-Queens II @
53 Maximum Subarray @@
54 Spiral Matrix @@
55 Jump Game @@
56 Merge Intervals @@@
57 Insert Interval @@
58 Length of Last Word @
59 Spiral Matrix II @@
60 Permutation Sequence @
61 Rotate List @
62 Unique Paths @@
63 Unique Paths II @
64 Minimum Path Sum @@
!!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 @@
82 Remove Duplicates from Sorted List II @@
83 Remove Duplicates from Sorted List @
84 Largest Rectangle in Histogram @
!85 Maximal Rectangle
86 Partition List @
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 @
96 Unique Binary Search Trees @@
98 Validate Binary Search Tree @@
100 Same Tree @
101 Symmetric Tree @@
102 Binary Tree Level Order Traversal @@
103 Binary Tree Zigzag Level Order Traversal @@
104 Maximum Depth of Binary Tree @@
105 Construct Binary Tree from Preorder and Inorder Traversal @@
106 Construct Binary Tree from Inorder and Postorder Traversal @@
107 Binary Tree Level Order Traversal II @@
108 Convert Sorted Array to Binary Search 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 @@
115 Distinct Subsequences @@
116 Populating Next Right Pointers in Each Node @@
117 Populating Next Right Pointers in Each Node II @@
118 Pascal's Triangle @
119 Pascal's Triangle II @
120 Triangle @
121 Best Time to Buy and Sell Stock @@@@
122 Best Time to Buy and Sell Stock II @@
!123 Best Time to Buy and Sell Stock III
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 @@
130 Surrounded Regions @@
131 Palindrome Partitioning @@
133 Clone Graph @@
134 Gas Station @@
136 Single Number @@
138 Copy List with Random Pointer @@
139 Word Break @@@@
140 Word Break II @
141 Linked List Cycle @@
142 Linked List Cycle II @@
143 Reorder List @@
144 Binary Tree Preorder Traversal @@
145 Binary Tree Postorder Traversal @@
146 LRU Cache @@
147 Insertion Sort List @@
!149 Max Points on a Line
150 Evaluate Reverse Polish Notation @@
151 Reverse Words in a String @@
152 Maximum Product Subarray @@
153 Find Minimum in Rotated Sorted Array @@
154 Find Minimum in Rotated Sorted Array II @@
155 Min Stack @@
157 Read N Characters Given Read4 @@
!158 Read N Characters Given Read4 II - Call multiple times
160 Intersection of Two Linked Lists @
161 One Edit Distance @@
162 Find Peak Element @@
163 Missing Ranges @@
165 Compare Version Numbers @@
166 Fraction to Recurring Decimal @
167 Two Sum II - Input array is sorted @@
168 Excel Sheet Column Title @@
169 Majority Element @
170 Two Sum III - Data structure design @@
171 Excel Sheet Column Number @@
172 Factorial Trailing Zeroes @
173 Binary Search Tree Iterator @@
!174 Dungeon Game
175 Combine Two Tables @
176 Second Highest Salary @
177 Nth Highest Salary @
179 Largest Number @
181 Employees Earning More Than Their Managers @
182 Duplicate Emails @
183 Customers Who Never Order @
184 Department Highest Salary @
186 Reverse Words in a String II @@
187 Repeated DNA Sequences @
!188 Best Time to Buy and Sell Stock IV
189 Rotate Array @@
190 Reverse Bits @
191 Number of 1 Bits @@
196 Delete Duplicate Emails @
197 Rising Temperature @
198 House Robber @@
199 Binary Tree Right Side View @@
200 Number of Islands @@
201 Bitwise AND of Numbers Range @
202 Happy Number @@
203 Remove Linked List Elements @@
204 Count Primes @@
205 Isomorphic Strings @@
206 Reverse Linked List @@
207 Course Schedule @@@
208 Implement Trie (Prefix Tree) @@
209 Minimum Size Subarray Sum @
210 Course Schedule II @
211 Add and Search Word - Data structure design @@
212 Word Search II @@
213 House Robber II @
!214 Shortest Palindrome
215 Kth Largest Element in an Array @@
216 Combination Sum III @
217 Contains Duplicate @@
!218 The Skyline Problem
219 Contains Duplicate II @
220 Contains Duplicate III @@
221 Maximal Square @
222 Count Complete Tree Nodes @
224 Basic Calculator @@
225 Implement Stack using Queues @
226 Invert Binary Tree @
227 Basic Calculator II @@
228 Summary Ranges @@
230 Kth Smallest Element in a BST @
231 Power of Two @
232 Implement Queue using Stacks @
235 Lowest Common Ancestor of a Binary Search Tree @@
236 Lowest Common Ancestor of a Binary Tree @@
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 @
234 Palindrome Linked List @
244 Shortest Word Distance II @
245 Shortest Word Distance III @
249 Group Shifted Strings @@
250 Count Univalue Subtrees @
251 Flatten 2D Vector @
252 Meeting Rooms @
253 Meeting Rooms II @@@
254 Factor Combinations @
256 Paint House @
257 Binary Tree Paths @
261 Graph Valid Tree @
263 Ugly Number @
264 Ugly Number II @
265 Paint House 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
276 Paint Fence @
277 Find the Celebrity @
278 First Bad Version @
279 Perfect Squares @@
280 Wiggle Sort @
!282 Expression Add Operators
283 Move Zeroes @@
284 Peeking Iterator @
285 Inorder Successor in BST @
286 Walls and Gates @
287 Find the Duplicate Number @
288 Unique Word Abbreviation @@
289 Game of Life @@
290 Word Pattern @
!291 Word Pattern II
293 Flip Game @
!294 Flip Game II
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 @@@
!302 Smallest Rectangle Enclosing Black Pixels
!305 Number of Islands II
307 Range Sum Query - Mutable @
!308 Range Sum Query 2D - Mutable
309 Best Time to Buy and Sell Stock with Cooldown @@
!311 Sparse Matrix Multiplication
312 Burst Balloons @
314 Binary Tree Vertical Order Traversal @
316 Remove Duplicate Letters @
!317 Shortest Distance from All Buildings
318 Maximum Product of Word Lengths @
322 Coin Change @@@
!323 Number of Connected Components in an Undirected Graph
324 Wiggle Sort II @
325 Maximum Size Subarray Sum Equals k @@
326 Power of Three @
329 Longest Increasing Path in a Matrix @
332 Reconstruct Itinerary @
334 Increasing Triplet Subsequence @
!336 Palindrome Pairs
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 @@
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 @@
!351 Android Unlock Patterns
!352 Data Stream as Disjoint Intervals
!353 Design Snake Game
354 Russian Doll Envelopes @
355 Design Twitter @
359 Logger Rate Limiter @@
361 Bomb Enemy @
362 Design Hit Counter @
364 Nested List Weight Sum II @
367 Valid Perfect Square @@
374 Guess Number Higher or Lower @
375 Guess Number Higher or Lower II @
376 Wiggle Subsequence @
377 Combination Sum IV @
378 Kth Smallest Element in a Sorted Matrix @
!379 Design Phone Directory
380 Insert Delete GetRandom O(1) @@@
381 Insert Delete GetRandom O(1) - Duplicates allowed @
384 Shuffle an Array @
!385 Mini Parser
386 Lexicographical Numbers @
387 First Unique Character in a String @@
389 Find the Difference @@
390 Elimination Game @
392 Is Subsequence @
394 Decode String @@@
395 Longest Substring with At Least K Repeating Characters @
398 Random Pick Index @
406 Queue Reconstruction by Height @
412 Fizz Buzz @
415 Add Strings @
417 Pacific Atlantic Water Flow @
421 Maximum XOR of Two Numbers in an Array @
426 Convert Binary Search Tree to Sorted Doubly Linked List @
428 Serialize and Deserialize N-ary Tree @
429 N-ary Tree Level Order Traversal @
431 Encode N-ary Tree to Binary Tree @
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 @
449 Serialize and Deserialize BST @
454 4Sum II @@
459 Repeated Substring Pattern @
460 LFU Cache @
463 Island Perimeter @
509 Fibonacci Number @
518 Coin Change 2 @
528 Random Pick with Weight @
529 Minesweeper @
535 Encode and Decode TinyURL @
543 Diameter of Binary Tree @
559 Maximum Depth of N-ary Tree @
560 Subarray Sum Equals K @
589 N-ary Tree Preorder Traversal @
590 N-ary Tree Postorder Traversal @@
599 Minimum Index Sum of Two Lists @
609 Find Duplicate File in System @
621 Task Scheduler @@
635 Design Log Storage System @
642 Design Search Autocomplete System @@@
647 Palindromic Substrings @
648 Replace Words @
652 Find Duplicate Subtrees @
653 Two Sum IV - Input is a BST @
657 Robot Return to Origin @
658 Find K Closest Elements @
675 Cut Off Trees for Golf Event @@
677 Map Sum Pairs @
692 Top K Frequent Words @
695 Max Area of Island @
700 Search in a Binary Search Tree @
705 Design HashSet @
706 Design HashMap @@
708 Insert into a Cyclic Sorted List @
713 Subarray Product Less Than K @
716 Max Stack @
721 Accounts Merge @
733 Flood Fill @
735 Asteroid Collision @
739 Daily Temperatures @
755 Pour Water @
763 Partition Labels @@
767 Reorganize String @
771 Jewels and Stones @@
773 Sliding Puzzle @
776 Split BST @
788 Rotated Digits @
791 Custom Sort String @
811 Subdomain Visit Count @
819 Most Common Word @@@
829 Consecutive Numbers Sum @
832 Flipping an Image @
836 Rectangle Overlap @
841 Keys and Rooms @
849 Maximize Distance to Closest Person @
868 Binary Gap @
895 Maximum Frequency Stack @
904 Fruit Into Baskets @@
905 Sort Array By Parity @
906 Super Palindromes @
907 Sum of Subarray Minimums @
909 Snakes and Ladders @
923 3Sum With Multiplicity @
929 Unique Email Addresses @
935 Knight Dialer @
937 Reorder Log Files @@
947 Most Stones Removed with Same Row or Column @
953 Verifying an Alien Dictionary @
957 Prison Cells After N Days @
966 Vowel Spellchecker @
973 K Closest Points to Origin @@@
974 Subarray Sums Divisible by K @
977 Squares of a Sorted Array @@
981 Time Based Key-Value Store @
986 Interval List Intersections @
987 Vertical Order Traversal of a Binary Tree @
1041 Robot Bounded In Circle @
1042 Flower Planting With No Adjacent @
1043 Partition Array for Maximum Sum @
1046 Last Stone Weight @
1048 Longest String Chain @
1049 Last Stone Weight II @
1051 Height Checker @
1052 Grumpy Bookstore Owner @
1053 Previous Permutation With One Swap @
1054 Distant Barcodes @
1055 Shortest Way to Form String @
1056 Confusing Number @
1057 Campus Bikes @
1059 All Paths from Source Lead to Destination @
1060 Missing Element in Sorted Array @
1061 Lexicographically Smallest Equivalent String @
1062 Longest Repeating Substring @
1064 Fixed Point @
1065 Index Pairs of a String @
1071 Greatest Common Divisor of Strings @
1072 Flip Columns For Maximum Number of Equal Rows @
1073 Adding Two Negabinary Numbers @
1078 Occurrences After Bigram @
1079 Letter Tile Possibilities @
1081 Smallest Subsequence of Distinct Characters @
1085 Sum of Digits in the Minimum Number @
1086 High Five @
1087 Brace Expansion @
1089 Duplicate Zeros @@
1090 Largest Values From Labels @
1091 Shortest Path in Binary Matrix @
1094 Car Pooling @
1128 Number of Equivalent Domino Pairs @