LeetCode

https://leetcode.com

July LeetCoding Challenge

Click here for problem descriptions.

Solutions in various programming languages are provided. Enjoy it.

1. Arranging Coins: Maths
2. Binary Tree Level Order Traversal II: DFS
3. Prison Cells After N Days: Maths
4. Ugly Number II: DP
5. Hamming Distance: Bitwise Manipulation
6. Plus One: Maths
7. Island Perimeter: BFS
8. 3Sum: Two pointers
9. Maximum Width of Binary Tree: DFS
10. Flatten a Multilevel Doubly Linked List: Queue
11. Subsets: DP
12. Reverse Bits: Bitwise
13. Same Tree: DFS
14. Angle Between Hands of a Clock: Math
15. Reverse Words in a String: Pointer
16. Pow(x,n): Recursion
17. Top K Frequent Elements: Bucket
18. Course Schedule II: BFS
19. Add Binary
20. Remove Linked List Elements
21. Word Search
22. Binary Tree Zigzag Level Order Traversal
23. Single Number III
24. All Paths From Source to Target
25. Find Minimum in Rotated Sorted Array II
26. Add Digits
27. Construct Binary Tree from Inorder and Postorder Traversal
28. Task Scheduler
29. Best Time to Buy and Sell Stock with Cooldown: State machine

June LeetCoding Challenge

Click here for problem descriptions.

Solutions in various programming languages are provided. Enjoy it.

1. Invert Binary Tree: Tree Traversal
2. Delete Node in a Linked List: Linked List
3. Two City Scheduling: DP
4. Reverse String: String
5. Random Pick With Weight: Binary Search + Probability
6. Queue Reconstruction by Height: Greedy
7. Coin Change 2: DP
8. Power of Two: Bitwise manipulation
9. Is Subsequence: Two pointers / DP
10. Search Insert Position: Binary Search
11. Sort Colors: Two Pointers
12. Insert Delete GetRandom: Hash Table
13. Largest Divisible Subset: DP
14. Cheapest Flights Within K Stops: DP
15. Search in a Binary Search Tree: Recursive
16. Validate IP Address: String
17. Surrounded Regions: BFS
18. H Index II: Binary Search
19. Longest Duplicate Substring:
20. Permutation Sequence: Maths
21. Dungeon Game: DP
22. Single Number II: Bitwise Manipulation
23. Count Complete Tree Nodes: Tree Traversal
24. Unique Binary Search Trees: DP
25. Find the Duplicate Number: Cycle Detect
26. Sum Root To Leaf Numbers: DFS
27. Perfect Squares: DP
28. Reconstruct Itinerary: DFS
29. Unique Paths: DP
30. Word Search: Trie + DFS

May LeetCoding Challenge

Click here for problem descriptions.

Solutions in various programming languages are provided. Enjoy it.

1. First Bad String: Binary search.
2. Jewels and Stones: Hash Table
3. Ransom Note: Hash Table
4. Number Complement: Bitwise Manipulation
5. First Unique Character In a String: Hash Table
6. Majority Element: Ad hoc
7. Cousins in Binary Tree: BFS / Recursion
8. Check if it is straight line: Cross Product
9. Valid Perfect Square: Math
10. Find the Town Judge: Graph Theory
11. Flood Fill: BFS
12. Single Element In a Sorted Array: Binary Search
13. Remove K Digits: Greedy
14. Implement Trie: Trie
15. Maximum Sum Circular Subarray: DP
16. Odd Even Linked List: Linked List
17. Find All Anagrams in a String: Sliding window + Hash Table
18. Permutation In String: Sliding window + Hash Table
19. Online Stock Span: DP
20. Kth-Smallest-Element-In-A-BST: BST
21. Count Square Submatrices with All Ones: DP
22. Sort Characters By Frequency: Hash Table
23. Interval List Intersections: Two Pointers
24. Construct Binary Search Tree from Preorder Traversal: Binary Search Tree
25. Uncrossed Lines: DP
26. Contiguous Array: Hash Table
27. Possible Bipartition: Bipartite Graph
28. Counting Bits: Math
29. Course Schedule: Topological Sort
30. K Closest Points to Origin: Priority_queue, Sort
31. Edit Distance: DP

30-Day (April) LeetCoding Challenge

Click here for problem descriptions.

1. Single Number: Bitwise Manipulation
2. Happy Number: Implementation
3. Maximum Subarray: DP
4. Move Zeros: Two pointers
5. Best Time to Buy and Sell Stock II: Greedy
6. Group Anagrams: Hash Table