Apple

#	Title	Difficulty	Frequency
1	Two Sum	Easy	29.23
2	Add Two Numbers	Medium	5.44
3	Longest Substring Without Repeating Characters	Medium	13.31
4	Median of Two Sorted Arrays	Hard	6.32
5	Longest Palindromic Substring	Medium	9.42
6	Zigzag Conversion	Medium	5.28
7	Reverse Integer	Medium	7.19
8	String to Integer (atoi)	Medium	5.79
9	Palindrome Number	Easy	5.63
11	Container With Most Water	Medium	1.45
12	Integer to Roman	Medium	2.33
13	Roman to Integer	Easy	51.13
14	Longest Common Prefix	Easy	15.31
15	3Sum	Medium	3.58
17	Letter Combinations of a Phone Number	Medium	9.35
19	Remove Nth Node From End of List	Medium	2.22
20	Valid Parentheses	Easy	8.93
21	Merge Two Sorted Lists	Easy	5.56
22	Generate Parentheses	Medium	3.24
23	Merge k Sorted Lists	Hard	2.03
26	Remove Duplicates from Sorted Array	Easy	1.86
27	Remove Element	Easy	0.56
31	Next Permutation	Medium	6.18
32	Longest Valid Parentheses	Hard	13.65
33	Search in Rotated Sorted Array	Medium	0.52
34	Find First and Last Position of Element in Sorted Array	Medium	1.09
35	Search Insert Position	Easy	0.83
36	Valid Sudoku	Medium	12.59
37	Sudoku Solver	Hard	9.36
38	Count and Say	Medium	11.12
41	First Missing Positive	Hard	2.75
42	Trapping Rain Water	Hard	10.58
46	Permutations	Medium	2.99
48	Rotate Image	Medium	14.98
49	Group Anagrams	Medium	0.84
50	Pow(x, n)	Medium	2.25
53	Maximum Subarray	Medium	4.31
54	Spiral Matrix	Medium	3.60
56	Merge Intervals	Medium	10.03
62	Unique Paths	Medium	3.11
64	Minimum Path Sum	Medium	5.54
66	Plus One	Easy	2.07
69	Sqrt(x)	Easy	2.61
70	Climbing Stairs	Easy	0.67
73	Set Matrix Zeroes	Medium	1.30
78	Subsets	Medium	1.48
80	Remove Duplicates from Sorted Array II	Medium	5.68
81	Search in Rotated Sorted Array II	Medium	0.18
88	Merge Sorted Array	Easy	5.95
98	Validate Binary Search Tree	Medium	1.14
104	Maximum Depth of Binary Tree	Easy	1.73
118	Pascal's Triangle	Easy	3.60
120	Triangle	Medium	3.33
121	Best Time to Buy and Sell Stock	Easy	5.64
122	Best Time to Buy and Sell Stock II	Medium	1.36
124	Binary Tree Maximum Path Sum	Hard	7.78
125	Valid Palindrome	Easy	0.60
127	Word Ladder	Hard	3.58
128	Longest Consecutive Sequence	Medium	1.94
131	Palindrome Partitioning	Medium	3.42
136	Single Number	Easy	2.32
138	Copy List with Random Pointer	Medium	10.02
139	Word Break	Medium	5.11
146	LRU Cache	Medium	8.12
148	Sort List	Medium	3.72
151	Reverse Words in a String	Medium	1.10
152	Maximum Product Subarray	Medium	3.23
155	Min Stack	Medium	1.44
162	Find Peak Element	Medium	3.61
169	Majority Element	Easy	1.46
179	Largest Number	Medium	6.83
189	Rotate Array	Medium	8.88
191	Number of 1 Bits	Easy	4.94
198	House Robber	Medium	1.14
200	Number of Islands	Medium	5.78
202	Happy Number	Easy	8.01
206	Reverse Linked List	Easy	5.65
207	Course Schedule	Medium	6.11
210	Course Schedule II	Medium	2.83
215	Kth Largest Element in an Array	Medium	5.66
217	Contains Duplicate	Easy	5.66
226	Invert Binary Tree	Easy	1.25
227	Basic Calculator II	Medium	8.39
234	Palindrome Linked List	Easy	22.15
235	Lowest Common Ancestor of a Binary Search Tree	Medium	4.56
237	Delete Node in a Linked List	Medium	2.80
238	Product of Array Except Self	Medium	4.14
253	Meeting Rooms II	Medium	7.52
273	Integer to English Words	Hard	50.26
283	Move Zeroes	Easy	1.84
290	Word Pattern	Easy	2.90
322	Coin Change	Medium	4.57
328	Odd Even Linked List	Medium	3.22
329	Longest Increasing Path in a Matrix	Hard	7.16
344	Reverse String	Easy	3.12
347	Top K Frequent Elements	Medium	11.41
395	Longest Substring with At Least K Repeating Characters	Medium	13.31
442	Find All Duplicates in an Array	Medium	4.81
443	String Compression	Medium	12.14
445	Add Two Numbers II	Medium	9.44
463	Island Perimeter	Easy	37.73
493	Reverse Pairs	Hard	4.74
560	Subarray Sum Equals K	Medium	10.57
584	Find Customer Referee	Easy	1.33
595	Big Countries	Easy	0.86
605	Can Place Flowers	Easy	1.22
619	Biggest Single Number	Easy	5.19
649	Dota2 Senate	Medium	16.99
692	Top K Frequent Words	Medium	7.47
714	Best Time to Buy and Sell Stock with Transaction Fee	Medium	6.01
733	Flood Fill	Easy	12.04
739	Daily Temperatures	Medium	12.99
703	Kth Largest Element in a Stream	Easy	4.28
704	Binary Search	Easy	3.83
796	Rotate String	Easy	5.71
706	Design HashMap	Easy	21.21
808	Soup Servings	Medium	26.29
622	Design Circular Queue	Medium	26.24
863	All Nodes Distance K in Binary Tree	Medium	6.70
875	Koko Eating Bananas	Medium	1.83
876	Middle of the Linked List	Easy	1.24
509	Fibonacci Number	Easy	5.24
981	Time Based Key-Value Store	Medium	10.06
1047	Remove All Adjacent Duplicates In String	Easy	10.66
1095	Find in Mountain Array	Hard	18.75
1289	Minimum Falling Path Sum II	Hard	21.71
1207	Unique Number of Occurrences	Easy	48.06
1344	Angle Between Hands of a Clock	Medium	32.28
1472	Design Browser History	Medium	14.31
1493	Longest Subarray of 1's After Deleting One Element	Medium	4.96
1480	Running Sum of 1d Array	Easy	1.92
1641	Count Sorted Vowel Strings	Medium	19.20
1672	Richest Customer Wealth	Easy	2.54
1710	Maximum Units on a Truck	Easy	19.11
1732	Find the Highest Altitude	Easy	7.69
1768	Merge Strings Alternately	Easy	2.39
1802	Maximum Value at a Given Index in a Bounded Array	Medium	59.76
1970	Last Day Where You Can Still Cross	Hard	54.31
2281	Sum of Total Strength of Wizards	Hard	43.18
2235	Add Two Integers	Easy	15.64
2352	Equal Row and Column Pairs	Medium	6.37
2418	Sort the People	Easy	10.19
2667	Create Hello World Function	Easy	4.37