LeetCode

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July LeetCoding Challenge

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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

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

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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