1. Valid Parentheses
2. Merge Two Sorted Lists
3. Single Number
4. Leaf-Similar Trees
5. Design HashMap
6. Logger Rate Limiter
7. Lemonade Change
8. Diameter of Binary Tree
9. Shortest Distance to a Character
10. Greatest Common Divisor of Strings
11. Valid Palindrome II
12. Backspace String Compare
13. Maximum Subarray
14. Symmetric Tree
15. Best Time to Buy and Sell Stock
16. Design Hit Counter
17. Kth Largest Element in an Array
18. Subsets
19. Validate Binary Search Tree
20. Maximum Average Subtree
21. Binary Search Tree Iterator
22. Peeking Iterator
23. Merge Intervals
24. Insert into a Binary Search Tree
25. Longest Substring Without Repeating Characters
26. Evaluate Reverse Polish Notation
27. Random Pick with Weight
28. Palindromic Substrings
29. Subarray Product Less Than K
30. Decode String
31. Meeting Rooms II
32. Single Element in a Sorted Array
33. Binary Tree Right Side View
34. Find Leaves of Binary Tree
35. Dice Roll Simulation
36. Permutations
37. Flatten Nested List Iterator
38. Generate Parentheses
39. Rank Teams by Votes
40. Longest Increasing Subsequence
41. Time Based Key-Value Store
42. Basic Calculator II
43. Number of Islands
44. Lowest Common Ancestor of a Binary Tree
45. Letter Combinations of a Phone Number
46. Top K Frequent Words
47. Binary Tree Level Order Traversal
48. Friend Circles
49. Next Permutation
50. Verbal Arithmetic Puzzle
51. Find Median from Data Stream
52. Merge k Sorted Lists
53. Best Time to Buy and Sell Stock III