Easy
- 1. Two Sum
- 9. Palindrome Number
- 13. Roman to Integer
- 14. Longest Common Prefix
- 20. Valid Parentheses
- 21. Merge Two Sorted Lists
- 26. Remove Duplicates from Sorted Array
- 27. Remove Element
- 35. Search Insert Position
- 58. Length Of Last words
- 66. Plus One
- 67. Add Binary
- 70. Climbing Stairs
- 83. Remove Duplicates from Sorted List
- 94. Binary Tree Inorder Traversal
- 100. Same Tree
- 108. Convert Sorted Array to Binary Search Tree
- 111. Minimum Depth of Binary Tree
- 112. Path Sum
- 118. Pascal’s Triangle
- 119. Pascal’s Triangle II
- 344. Reverse String
- 476. Number Complement
- 500. Keyboard Row
- 509. Fibonacci Number
- 538. Convert BST to Greater Tree
- 543. Diameter of Binary TreeDiameter of Binary Tree
- 589. N-ary Tree Preorder Traversal
- 590. N-ary Tree Postorder Traversal
- 654. Maximum Binary Tree
- 669. Trim a Binary Search Tree
- 728. Self Dividing Numbers
- 804. Unique Morse Code Words
- 806. Number of Lines To Write String
- 811. Subdomain Visit Count
- 821. Shortest Distance to a Character
- 832. Flipping an Image
- 893. Groups of Special-Equivalent Strings
- 897. Increasing Order Search Tree
- 908. Smallest Range I
- 938. Range Sum of BST
- 944. Delete Columns to Make Sorted
- 961. N-Repeated Element in Size 2N Array
- 965. Univalued Binary Tree
- 973. K Closest Points to Origin
- 977. Squares of a Sorted Array
- 993. Cousins in Binary Tree
- 999. Available Captures for Rook
- 1002. Find Common Characters
- 1480. Running Sum of 1d Array
- 1512. Number of Good Pairs
Medium
- 2. Add Two Numbers
- 3. Longest Substring Without Repeating Characters
- 5. Longest Palindromic Substring
- 6. Zigzag Conversion
- 7. Reverse Integer
- 8. String to Integer (atoi)
- 16. 3Sum Closest
- 17. Letter Combinations of a Phone Number
- 18. 4Sum
- 19. Remove Nth Node From End of List
- 22. Generate Parentheses
- 24. Swap Nodes in Pairs
- 27. Find the Index of the First Occurrence in a String
- 29. Divide Two Integers
- 30. Next Permutation
- 33. Search in Rotated Sorted Array
- 34. Find First and Last Position of Element in Sorted Array
- 36. Valid Sudoku
- 38. Count and Say
- 39. Combination Sum
- 40. Combination Sum II
- 43. Multiply Strings
- 45. Jump Game II
- 46. Permutations
- 47. Permutations II
- 48. Rotate Image
- 49. Group Anagrams
- 50. Pow
- 54. Spiral Matrix
- 55. Jump Game
- 56. Merge Intervals
- 57. Insert Intervals
- 59. Spiral Matrix II
- 61. Rotate List
- 62. Unique Paths
- 63. Unique Paths II
- 64. Minimum Path Sum
- 429. N-ary Tree Level Order Traversal
- 912. Sort an Array
- 985. Sum of Even Numbers After Queries
Hard
- 4. Median of Two Sorted Arrays
- 10. Regular Expression Matching
- 23. Merge k Sorted Lists
- 25. Reverse Nodes in k-Group
- 30. Substring With Concatenation Of All Words
- 32. Longest Valid Parentheses
- 37. Sudoku Solver
- 41. First Missing Positive
- 42. Trapping Rain Water
- 44. Wildcard Matching
- 51. N-Queens
- 52. N-Queens II
- 53. Maximum Subarray
- 60, Permutation Sequence
