Amazon

#	Title	Difficulty	Frequency
1	Two Sum	Easy	94.50
2	Add Two Numbers	Medium	44.49
3	Longest Substring Without Repeating Characters	Medium	33.32
4	Median of Two Sorted Arrays	Hard	27.44
5	Longest Palindromic Substring	Medium	59.14
6	Zigzag Conversion	Medium	5.28
7	Reverse Integer	Medium	15.51
8	String to Integer (atoi)	Medium	5.79
9	Palindrome Number	Easy	9.15
10	Regular Expression Matching	Hard	2.91
11	Container With Most Water	Medium	5.68
13	Roman to Integer	Easy	90.11
14	Longest Common Prefix	Easy	39.07
15	3Sum	Medium	25.12
16	3Sum Closest	Medium	3.13
17	Letter Combinations of a Phone Number	Medium	27.57
18	4Sum	Medium	19.46
19	Remove Nth Node From End of List	Medium	8.61
20	Valid Parentheses	Easy	26.43
21	Merge Two Sorted Lists	Easy	9.68
22	Generate Parentheses	Medium	12.39
23	Merge k Sorted Lists	Hard	4.50
24	Swap Nodes in Pairs	Medium	11.20
25	Reverse Nodes in k-Group	Hard	2.31
26	Remove Duplicates from Sorted Array	Easy	15.60
27	Remove Element	Easy	2.24
28	Find the Index of the First Occurrence in a String	Easy	4.89
31	Next Permutation	Medium	33.56
32	Longest Valid Parentheses	Hard	7.91
33	Search in Rotated Sorted Array	Medium	0.75
34	Find First and Last Position of Element in Sorted Array	Medium	1.09
35	Search Insert Position	Easy	3.29
36	Valid Sudoku	Medium	5.79
37	Sudoku Solver	Hard	24.11
38	Count and Say	Medium	5.10
39	Combination Sum	Medium	3.02
40	Combination Sum II	Medium	2.18
41	First Missing Positive	Hard	29.34
42	Trapping Rain Water	Hard	93.60
43	Multiply Strings	Medium	4.07
44	Wildcard Matching	Hard	8.59
45	Jump Game II	Medium	16.61
46	Permutations	Medium	1.34
48	Rotate Image	Medium	23.68
49	Group Anagrams	Medium	15.77
50	Pow(x, n)	Medium	8.72
51	N-Queens	Hard	3.31
53	Maximum Subarray	Medium	22.60
54	Spiral Matrix	Medium	58.63
55	Jump Game	Medium	15.00
56	Merge Intervals	Medium	30.36
57	Insert Interval	Medium	2.30
60	Permutation Sequence	Hard	6.59
61	Rotate List	Medium	2.34
62	Unique Paths	Medium	11.89
64	Minimum Path Sum	Medium	5.54
66	Plus One	Easy	3.65
67	Add Binary	Easy	7.18
69	Sqrt(x)	Easy	13.46
70	Climbing Stairs	Easy	5.85
72	Edit Distance	Medium	2.74
73	Set Matrix Zeroes	Medium	11.12
74	Search a 2D Matrix	Medium	1.51
75	Sort Colors	Medium	13.16
76	Minimum Window Substring	Hard	12.02
77	Combinations	Medium	6.33
78	Subsets	Medium	12.63
79	Word Search	Medium	4.50
80	Remove Duplicates from Sorted Array II	Medium	3.23
83	Remove Duplicates from Sorted List	Easy	3.84
84	Largest Rectangle in Histogram	Hard	24.45
87	Scramble String	Hard	19.20
88	Merge Sorted Array	Easy	16.56
90	Subsets II	Medium	2.24
92	Reverse Linked List II	Medium	7.03
94	Binary Tree Inorder Traversal	Easy	1.20
98	Validate Binary Search Tree	Medium	1.14
100	Same Tree	Easy	2.31
101	Symmetric Tree	Easy	6.16
102	Binary Tree Level Order Traversal	Medium	2.80
103	Binary Tree Zigzag Level Order Traversal	Medium	9.48
106	Construct Binary Tree from Inorder and Postorder Traversal	Medium	10.70
109	Convert Sorted List to Binary Search Tree	Medium	11.38
110	Balanced Binary Tree	Easy	3.16
111	Minimum Depth of Binary Tree	Easy	2.89
114	Flatten Binary Tree to Linked List	Medium	3.34
118	Pascal's Triangle	Easy	46.17
121	Best Time to Buy and Sell Stock	Easy	36.38
122	Best Time to Buy and Sell Stock II	Medium	1.36
124	Binary Tree Maximum Path Sum	Hard	11.90
126	Word Ladder II	Hard	20.53
127	Word Ladder	Hard	13.61
128	Longest Consecutive Sequence	Medium	23.39
131	Palindrome Partitioning	Medium	3.42
134	Gas Station	Medium	19.62
135	Candy	Hard	35.81
136	Single Number	Easy	1.04
137	Single Number II	Medium	12.89
138	Copy List with Random Pointer	Medium	21.28
139	Word Break	Medium	5.11
141	Linked List Cycle	Easy	0.84
143	Reorder List	Medium	10.33
145	Binary Tree Postorder Traversal	Easy	2.10
146	LRU Cache	Medium	63.83
148	Sort List	Medium	3.72
151	Reverse Words in a String	Medium	12.72
152	Maximum Product Subarray	Medium	5.67
155	Min Stack	Medium	12.29
160	Intersection of Two Linked Lists	Easy	1.92
162	Find Peak Element	Medium	13.72
169	Majority Element	Easy	18.07
171	Excel Sheet Column Number	Easy	6.54
176	Second Highest Salary	Medium	4.76
177	Nth Highest Salary	Medium	3.21
179	Largest Number	Medium	6.83
181	Employees Earning More Than Their Managers	Easy	3.76
183	Customers Who Never Order	Easy	1.93
189	Rotate Array	Medium	20.64
198	House Robber	Medium	6.92
199	Binary Tree Right Side View	Medium	1.55
200	Number of Islands	Medium	87.61
202	Happy Number	Easy	2.06
203	Remove Linked List Elements	Easy	6.20
204	Count Primes	Medium	7.30
206	Reverse Linked List	Easy	2.55
207	Course Schedule	Medium	22.48
208	Implement Trie (Prefix Tree)	Medium	6.28
209	Minimum Size Subarray Sum	Medium	2.09
213	House Robber II	Medium	2.83
214	Shortest Palindrome	Hard	33.77
215	Kth Largest Element in an Array	Medium	12.31
217	Contains Duplicate	Easy	4.19
219	Contains Duplicate II	Easy	2.30
226	Invert Binary Tree	Easy	1.25
229	Majority Element II	Medium	3.12
230	Kth Smallest Element in a BST	Medium	1.96
231	Power of Two	Easy	2.15
234	Palindrome Linked List	Easy	27.29
235	Lowest Common Ancestor of a Binary Search Tree	Medium	2.05
236	Lowest Common Ancestor of a Binary Tree	Medium	2.02
237	Delete Node in a Linked List	Medium	2.80
238	Product of Array Except Self	Medium	4.14
239	Sliding Window Maximum	Hard	17.34
242	Valid Anagram	Easy	3.19
253	Meeting Rooms II	Medium	16.19
263	Ugly Number	Easy	6.04
273	Integer to English Words	Hard	17.06
278	First Bad Version	Easy	2.81
279	Perfect Squares	Medium	12.52
283	Move Zeroes	Easy	5.02
287	Find the Duplicate Number	Medium	5.02
295	Find Median from Data Stream	Hard	8.03
297	Serialize and Deserialize Binary Tree	Hard	4.81
300	Longest Increasing Subsequence	Medium	3.14
309	Best Time to Buy and Sell Stock with Cooldown	Medium	5.08
312	Burst Balloons	Hard	16.99
319	Bulb Switcher	Medium	11.54
322	Coin Change	Medium	2.59
328	Odd Even Linked List	Medium	12.29
338	Counting Bits	Easy	5.97
344	Reverse String	Easy	3.12
347	Top K Frequent Elements	Medium	18.22
349	Intersection of Two Arrays	Easy	6.79
371	Sum of Two Integers	Medium	5.26
380	Insert Delete GetRandom O(1)	Medium	3.73
383	Ransom Note	Easy	6.73
387	First Unique Character in a String	Easy	3.68
410	Split Array Largest Sum	Hard	12.55
412	Fizz Buzz	Easy	28.62
416	Partition Equal Subset Sum	Medium	2.39
435	Non-overlapping Intervals	Medium	3.77
442	Find All Duplicates in an Array	Medium	18.01
443	String Compression	Medium	12.14
445	Add Two Numbers II	Medium	20.11
450	Delete Node in a BST	Medium	3.49
460	LFU Cache	Hard	15.66
486	Predict the Winner	Medium	16.96
493	Reverse Pairs	Hard	46.67
494	Target Sum	Medium	3.46
496	Next Greater Element I	Easy	10.91
506	Relative Ranks	Easy	17.28
516	Longest Palindromic Subsequence	Medium	5.04
517	Super Washing Machines	Hard	77.39
518	Coin Change II	Medium	1.44
540	Single Element in a Sorted Array	Medium	22.04
542	01 Matrix	Medium	4.02
543	Diameter of Binary Tree	Easy	3.14
547	Number of Provinces	Medium	16.82
560	Subarray Sum Equals K	Medium	43.14
561	Array Partition	Easy	7.97
567	Permutation in String	Medium	2.42
572	Subtree of Another Tree	Easy	2.73
584	Find Customer Referee	Easy	1.33
595	Big Countries	Easy	7.52
602	Friend Requests II: Who Has the Most Friends	Medium	10.03
605	Can Place Flowers	Easy	2.72
633	Sum of Square Numbers	Medium	17.51
649	Dota2 Senate	Medium	7.91
652	Find Duplicate Subtrees	Medium	22.44
658	Find K Closest Elements	Medium	23.26
662	Maximum Width of Binary Tree	Medium	27.05
680	Valid Palindrome II	Easy	4.48
695	Max Area of Island	Medium	4.57
714	Best Time to Buy and Sell Stock with Transaction Fee	Medium	6.01
721	Accounts Merge	Medium	7.59
724	Find Pivot Index	Easy	14.79
733	Flood Fill	Easy	18.22
735	Asteroid Collision	Medium	25.70
743	Network Delay Time	Medium	4.95
744	Find Smallest Letter Greater Than Target	Easy	21.71
746	Min Cost Climbing Stairs	Easy	8.13
754	Reach a Number	Medium	34.23
763	Partition Labels	Medium	8.57
767	Reorganize String	Medium	24.45
703	Kth Largest Element in a Stream	Easy	24.18
704	Binary Search	Easy	0.97
785	Is Graph Bipartite?	Medium	4.99
808	Soup Servings	Medium	26.29
707	Design Linked List	Medium	6.98
827	Making A Large Island	Hard	18.75
622	Design Circular Queue	Medium	12.52
852	Peak Index in a Mountain Array	Medium	39.31
863	All Nodes Distance K in Binary Tree	Medium	24.47
875	Koko Eating Bananas	Medium	20.44
876	Middle of the Linked List	Easy	14.21
877	Stone Game	Medium	12.25
901	Online Stock Span	Medium	23.43
907	Sum of Subarray Minimums	Medium	10.35
910	Smallest Range II	Medium	33.65
933	Number of Recent Calls	Easy	6.38
934	Shortest Bridge	Medium	49.78
937	Reorder Data in Log Files	Medium	33.36
946	Validate Stack Sequences	Medium	32.66
947	Most Stones Removed with Same Row or Column	Medium	14.52
974	Subarray Sums Divisible by K	Medium	13.44
981	Time Based Key-Value Store	Medium	4.60
987	Vertical Order Traversal of a Binary Tree	Hard	4.79
992	Subarrays with K Different Integers	Hard	30.43
993	Cousins in Binary Tree	Easy	20.59
1002	Find Common Characters	Easy	14.79
1009	Complement of Base 10 Integer	Easy	17.62
1060	Missing Element in Sorted Array	Medium	47.96
1019	Next Greater Node In Linked List	Medium	19.01
1020	Number of Enclaves	Medium	8.15
1027	Longest Arithmetic Subsequence	Medium	11.03
1035	Uncrossed Lines	Medium	16.43
1039	Minimum Score Triangulation of Polygon	Medium	23.78
1161	Maximum Level Sum of a Binary Tree	Medium	8.61
1046	Last Stone Weight	Easy	18.81
1071	Greatest Common Divisor of Strings	Easy	6.95
1092	Shortest Common Supersequence	Hard	21.61
1125	Smallest Sufficient Team	Hard	67.16
1143	Longest Common Subsequence	Medium	3.43
1207	Unique Number of Occurrences	Easy	29.72
1218	Longest Arithmetic Subsequence of Given Difference	Medium	10.19
1232	Check If It Is a Straight Line	Easy	65.36
1254	Number of Closed Islands	Medium	43.10
1251	Average Selling Price	Easy	8.58
2215	Find the Difference of Two Arrays	Easy	3.91
1268	Search Suggestions System	Medium	14.68
1280	Students and Examinations	Easy	3.02
2305	Fair Distribution of Cookies	Medium	42.09
1312	Minimum Insertion Steps to Make a String Palindrome	Hard	28.98
1337	The K Weakest Rows in a Matrix	Easy	16.16
1372	Longest ZigZag Path in a Binary Tree	Medium	8.50
1351	Count Negative Numbers in a Sorted Matrix	Easy	7.58
1376	Time Needed to Inform All Employees	Medium	15.97
1378	Replace Employee ID With The Unique Identifier	Easy	1.76
1431	Kids With the Greatest Number of Candies	Easy	9.87
1456	Maximum Number of Vowels in a Substring of Given Length	Medium	4.02
1470	Shuffle the Array	Easy	23.90
1472	Design Browser History	Medium	29.73
1491	Average Salary Excluding the Minimum and Maximum Salary	Easy	38.28
1492	The kth Factor of n	Medium	34.06
1493	Longest Subarray of 1's After Deleting One Element	Medium	18.53
1480	Running Sum of 1d Array	Easy	4.27
1498	Number of Subsequences That Satisfy the Given Sum Condition	Medium	16.43
1528	Shuffle String	Easy	6.68
1569	Number of Ways to Reorder Array to Get Same BST	Hard	111.02
1588	Sum of All Odd Length Subarrays	Easy	15.66
1603	Design Parking System	Easy	14.84
1581	Customer Who Visited but Did Not Make Any Transactions	Easy	8.77
1672	Richest Customer Wealth	Easy	2.54
1751	Maximum Number of Events That Can Be Attended II	Hard	48.55
1752	Check if Array Is Sorted and Rotated	Easy	28.75
1768	Merge Strings Alternately	Easy	6.51
1757	Recyclable and Low Fat Products	Easy	4.65
1823	Find the Winner of the Circular Game	Medium	11.64
1838	Frequency of the Most Frequent Element	Medium	21.21
1884	Egg Drop With 2 Eggs and N Floors	Medium	64.19
1903	Largest Odd Number in String	Easy	7.06
1929	Concatenation of Array	Easy	2.38
2024	Maximize the Confusion of an Exam	Medium	23.09
2055	Plates Between Candles	Medium	101.79
2090	K Radius Subarray Averages	Medium	34.43
2108	Find First Palindromic String in the Array	Easy	17.51
2141	Maximum Running Time of N Computers	Hard	19.29
2223	Sum of Scores of Built Strings	Hard	33.65
2272	Substring With Largest Variance	Hard	142.23
2244	Minimum Rounds to Complete All Tasks	Medium	63.25
2281	Sum of Total Strength of Wizards	Hard	121.78
2235	Add Two Integers	Easy	2.67
2328	Number of Increasing Paths in a Grid	Hard	36.43
2357	Make Array Zero by Subtracting Equal Amounts	Easy	21.36
2398	Maximum Number of Robots Within Budget	Hard	60.61
2385	Amount of Time for Binary Tree to Be Infected	Medium	39.82
2340	Minimum Adjacent Swaps to Make a Valid Array	Medium	97.27
2405	Optimal Partition of String	Medium	111.56
2355	Maximum Number of Books You Can Take	Hard	121.78
2448	Minimum Cost to Make Array Equal	Hard	32.81
2462	Total Cost to Hire K Workers	Medium	14.16
2542	Maximum Subsequence Score	Medium	26.08
2519	Count the Number of K-Big Indices	Hard	132.01
2551	Put Marbles in Bags	Hard	47.38
2660	Determine the Winner of a Bowling Game	Easy	33.65
2610	Convert an Array Into a 2D Array With Conditions	Medium	29.19
2620	Counter	Easy	1.90
2619	Array Prototype Last	Easy	17.73
2629	Function Composition	Easy	13.47
2719	Count of Integers	Hard	52.45
2622	Cache With Time Limit	Medium	17.67
2684	Maximum Number of Moves in a Grid	Medium	62.35
2742	Painting the Walls	Hard	51.08
2667	Create Hello World Function	Easy	4.37
2735	Collecting Chocolates	Medium	66.90
2769	Find the Maximum Achievable Number	Easy	7.38
2781	Length of the Longest Valid Substring	Hard	66.65