September 2022

1. Count Good Nodes in Binary Tree [Kotlin] [Haskell]

2. Average of Levels in Binary Tree [Kotlin] [Haskell]

3. Numbers With Same Consecutive Differences [Kotlin] [Haskell]

4. Vertical Order Traversal of a Binary Tree [Kotlin]

5. N-ary Tree Level Order Traversal [Kotlin]

6. Binary Tree Pruning [Kotlin]

7. Construct String from Binary Tree [Kotlin]

8. Binary Tree Inorder Traversal [Kotlin]

9. The Number of Weak Characters in the Game [Kotlin]

10. Best Time to Buy and Sell Stock IV [Kotlin]

11. Maximum Performance of a Team [Kotlin]

12. Bag of Tokens [Kotlin]

13. UTF-8 Validation [Kotlin]

14. Pseudo-Palindromic Paths in a Binary Tree [Kotlin] [Haskell]

15. Find Original Array From Doubled Array [Kotlin]

16. Maximum Score from Performing Multiplication Operations [Kotlin]

17. Palindrome Pairs [Kotlin]

18. Trapping Rain Water [Kotlin] [Haskell]

19. Find Duplicate File in System [Kotlin]

20. Maximum Length of Repeated Subarray [Kotlin]

21. Sum of Even Numbers After Queries [Kotlin]

22. Reverse Words in a String III [Kotlin]

23. Concatenation of Consecutive Binary Numbers [Kotlin] [Haskell]

24. Path Sum II [Kotlin]

25. Design Circular Queue [Kotlin]

26. Satisfiability of Equality Equations [Kotlin]

27. Push Dominoes [Kotlin] [Haskell]

28. Remove Nth Node From End of List [Kotlin]

29. Find k closest elements [Kotlin] [Haskell]

30. The Skyline Problem [Kotlin] [Haskell]

October 2022

1. Decode Ways [Kotlin] [Haskell]

2. Number of Dice Rolls With Target Sum [Kotlin] [Haskell]

3. Minimum Time to Make Rope Colorful [Kotlin] [Haskell]

4. Path Sum [Kotlin] [Haskell]

5. Add One Row to Tree [Kotlin] [Haskell]

6. Time Based Key-Value Store [Kotlin]

7. My Calendar III [Kotlin]

8. 3Sum Closest [Kotlin] [Haskell]

9. Two Sum IV - Input is a BST [Kotlin] [Haskell]

10. Break a Palindrome [Kotlin] [Haskell]

11. Increasing Triplet Subsequence [Kotlin] [Haskell]

12. Largest Perimeter Triangle [Kotlin] [Haskell]

13. Delete Node in a Linked List [Kotlin]

14. Delete the Middle Node of a Linked List [Kotlin] [Haskell]

15. String Compression II

16. Minimum Difficulty of a Job Schedule

17. Check if the Sentence Is Pangram [Kotlin]

18. Count and Say [Kotlin] [Haskell]

19. Top K Frequent Words

20. Integer to Roman [Kotlin] [Haskell]

21. Contains Duplicate II

22. Minimum Window Substring

23. Set Mismatch [Kotlin] [Haskell]

24. Maximum Length of a Concatenated String with Unique Characters

25. Check If Two String Arrays are Equivalent [Kotlin] [Haskell]

26. Continuous Subarray Sum

27. Image Overlap

28. Group Anagrams

29. Earliest Possible Day of Full Bloom

30. Shortest Path in a Grid with Obstacles Elimination

31. Toeplitz Matrix [Kotlin]

November 2022

1. Where Will the Ball Fall [Kotlin]

2. Minimum Genetic Mutation [Kotlin]

3. Longest Palindrome by Concatenating Two Letter Words

4. Reverse Vowels of a String [Kotlin] [Haskell]

5. Word Search II

6. Orderly Queue [Kotlin] [Haskell]

7. Maximum 69 Number

8. Make The String Great [Kotlin] [Haskell]

9. Online Stock Span

10. Remove All Adjacent Duplicates In String [Kotlin] [Haskell]

11. Remove Duplicates from Sorted Array [Kotlin] [Haskell]

12. Find Median from Data Stream

13. Reverse Words in a String [Kotlin] [Haskell]

14. Most Stones Removed with Same Row or Column

15. Count Complete Tree Nodes

16. Guess Number Higher or Lower [Kotlin]

17. Rectangle Area [Kotlin]

18. Ugly Number [Kotlin]

19. Erect the Fence.

20. Basic Calculator.

21. Nearest Exit from Entrance in Maze.

22. Perfect Squares [Kotlin]

23. Valid Sudoku [Kotlin]

24.

25.

26.

27.

28.

29.

30.

Basic data structures

• Linked list [Kotlin]

• Binary Tree [Kotlin]

• Prefix tree (trie) [Kotlin]

• Union-find (disjoint-set) [Kotlin]