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1.Two Sum
Easy
2.Add Two Numbers
Med.
3.Longest Substring Without Repeating Characters
Med.
4.Median of Two Sorted Arrays
Hard
5.Longest Palindromic Substring
Med.
6.Zigzag Conversion
Med.
7.Reverse Integer
Med.
8.String to Integer (atoi)
Med.
9.Palindrome Number
Easy
10.Regular Expression Matching
Hard
11.Container With Most Water
Med.
12.Integer to Roman
Med.
13.Roman to Integer
Easy
14.Longest Common Prefix
Easy
15.3Sum
Med.
16.3Sum Closest
Med.
17.Letter Combinations of a Phone Number
Med.
18.4Sum
Med.
19.Remove Nth Node From End of List
Med.
20.Valid Parentheses
Easy
21.Merge Two Sorted Lists
Easy
22.Generate Parentheses
Med.
23.Merge k Sorted Lists
Hard
24.Swap Nodes in Pairs
Med.
25.Reverse Nodes in k-Group
Hard
26.Remove Duplicates from Sorted Array
Easy
27.Remove Element
Easy
28.Find the Index of the First Occurrence in a String
Easy
29.Divide Two Integers
Med.
30.Substring with Concatenation of All Words
Hard
31.Next Permutation
Med.
32.Longest Valid Parentheses
Hard
33.Search in Rotated Sorted Array
Med.
34.Find First and Last Position of Element in Sorted Array
Med.
35.Search Insert Position
Easy
36.Valid Sudoku
Med.
37.Sudoku Solver
Hard
38.Count and Say
Med.
39.Combination Sum
Med.
40.Combination Sum II
Med.
41.First Missing Positive
Hard
42.Trapping Rain Water
Hard
43.Multiply Strings
Med.
44.Wildcard Matching
Hard
45.Jump Game II
Med.
46.Permutations
Med.
47.Permutations II
Med.
48.Rotate Image
Med.
49.Group Anagrams
Med.
50.Pow(x, n)
Med.