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Leetcode solutions in C++, C#, Python, Java, Scala, JS, Kotlin, Go, etc

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# LeetCode

https://leetcode.com

## November LeetCoding Challenge
Click [here](https://leetcode.com/explore/challenge/card/november-leetcoding-challenge/) for problem descriptions.

Solutions in various programming languages are provided. Enjoy it.

1. [Convert Binary Number in a Linked List to Integer](https://github.com/AlgoStudyGroup/Leetcode/tree/master/November-LeetCoding-Challenge/01-Convert-Binary-Number-in-a-Linked-List-to-Integer)
2. [Insertion Sort List](https://github.com/AlgoStudyGroup/Leetcode/tree/master/November-LeetCoding-Challenge/02-Insertion-Sort-List)
3. [Consecutive Characters](https://github.com/AlgoStudyGroup/Leetcode/tree/master/November-LeetCoding-Challenge/03-Consecutive-Characters)
4. [Minimum Height Trees](https://github.com/AlgoStudyGroup/Leetcode/tree/master/November-LeetCoding-Challenge/04-Minimum-Height-Trees)
5. [Minimum Cost to Move Chips to The Same Position](https://github.com/AlgoStudyGroup/Leetcode/tree/master/November-LeetCoding-Challenge/05-Minimum-Cost-to-Move-Chips-to-The-Same-Position)
6. [Find the Smallest Divisor Given a Threshold](https://github.com/AlgoStudyGroup/Leetcode/tree/master/November-LeetCoding-Challenge/06-Find-the-Smallest-Divisor-Given-a-Threshold)
7. [Add Two Numbers II](https://github.com/AlgoStudyGroup/Leetcode/tree/master/November-LeetCoding-Challenge/07-Add-Two-Numbers-II)
8. [Binary Tree Tilt](https://github.com/AlgoStudyGroup/Leetcode/tree/master/November-LeetCoding-Challenge/08-Binary-Tree-Tilt)
9. [Maximum Difference Between Node and Ancestor](https://github.com/AlgoStudyGroup/Leetcode/tree/master/November-LeetCoding-Challenge/09-Maximum-Difference-Between-Node-and-Ancestor)
10. [Flipping an Image](https://github.com/AlgoStudyGroup/Leetcode/tree/master/November-LeetCoding-Challenge/10-Flipping-an-Image)
11. [Valid Square](https://github.com/AlgoStudyGroup/Leetcode/tree/master/November-LeetCoding-Challenge/11-Valid-Square)
12. [Permutations II](https://github.com/AlgoStudyGroup/Leetcode/tree/master/November-LeetCoding-Challenge/12-Permutations-II)
13. [Populating Next Right Pointers in Each Node](https://github.com/AlgoStudyGroup/Leetcode/tree/master/November-LeetCoding-Challenge/13-Populating-Next-Right-Pointers-in-Each-Node)
14. [Poor Pigs](https://github.com/AlgoStudyGroup/Leetcode/tree/master/November-LeetCoding-Challenge/14-Poor-Pigs)
15. [Range Sum of BST](https://github.com/AlgoStudyGroup/Leetcode/tree/master/November-LeetCoding-Challenge/15-Range-Sum-of-BST)
16. [Longest Mountain in Array](https://github.com/AlgoStudyGroup/Leetcode/tree/master/November-LeetCoding-Challenge/16-Longest-Mountain-in-Array)
17. [Mirror Reflection](https://github.com/AlgoStudyGroup/Leetcode/tree/master/November-LeetCoding-Challenge/17-Mirror-Reflection)
18. [Merge Intervals](https://github.com/AlgoStudyGroup/Leetcode/tree/master/November-LeetCoding-Challenge/18-Merge-Intervals)
19. [Decode String](https://github.com/AlgoStudyGroup/Leetcode/tree/master/November-LeetCoding-Challenge/19-Decode-String)
20. [Search in Rotated Sorted Array II](https://github.com/AlgoStudyGroup/Leetcode/tree/master/November-LeetCoding-Challenge/20-Search-in-Rotated-Sorted-Array-II)
21. [Numbers At Most N Given Digit Set](https://github.com/AlgoStudyGroup/Leetcode/tree/master/November-LeetCoding-Challenge/21-Numbers-At-Most-N-Given-Digit-Set)
22. [Unique Morse Code Words](https://github.com/AlgoStudyGroup/Leetcode/tree/master/November-LeetCoding-Challenge/22-Unique-Morse-Code-Words)

## October LeetCoding Challenge
Click [here](https://leetcode.com/explore/challenge/card/october-leetcoding-challenge/) for problem descriptions.

Solutions in various programming languages are provided. Enjoy it.

1. [Number of Recent Calls](https://github.com/AlgoStudyGroup/Leetcode/tree/master/October-LeetCoding-Challenge/01-Number-of-Recent-Calls) : Queue
2. [Combination Sum](https://github.com/AlgoStudyGroup/Leetcode/tree/master/October-LeetCoding-Challenge/02-Combination-Sum)
3. [K-diff Pairs in an Array](https://github.com/AlgoStudyGroup/Leetcode/tree/master/October-LeetCoding-Challenge/03-K-diff-Pairs-in-an-Array)
4. [Remove Covered Intervals](https://github.com/AlgoStudyGroup/Leetcode/tree/master/October-LeetCoding-Challenge/04-Remove-Covered-Intervals)
5. [Complement of Base 10 Integer](https://github.com/AlgoStudyGroup/Leetcode/tree/master/October-LeetCoding-Challenge/05-Complement-of-Base-10-Integer)
6. [Insert into a Binary Search Tree](https://github.com/AlgoStudyGroup/Leetcode/tree/master/October-LeetCoding-Challenge/06-Insert-into-a-Binary-Search-Tree)
7. [Rotate List](https://github.com/AlgoStudyGroup/Leetcode/tree/master/October-LeetCoding-Challenge/07-Rotate-List)
8. [Binary Search](https://github.com/AlgoStudyGroup/Leetcode/tree/master/October-LeetCoding-Challenge/08-Binary-Search)
9. [Serialize and Deserialize BST](https://github.com/AlgoStudyGroup/Leetcode/tree/master/October-LeetCoding-Challenge/09-Serialize-and-Deserialize-BST)
10. [Minimum Number of Arrows to Burst Balloons](https://github.com/AlgoStudyGroup/Leetcode/tree/master/October-LeetCoding-Challenge/10-Minimum-Number-of-Arrows-to-Burst-Balloons)
11. [Remove Duplicate Letters](https://github.com/AlgoStudyGroup/Leetcode/tree/master/October-LeetCoding-Challenge/11-Remove-Duplicate-Letters)
12. [Buddy Strings](https://github.com/AlgoStudyGroup/Leetcode/tree/master/October-LeetCoding-Challenge/12-Buddy-Strings)
13. [Sort List](https://github.com/AlgoStudyGroup/Leetcode/tree/master/October-LeetCoding-Challenge/13-Sort-List)
14. [House Robber II](https://github.com/AlgoStudyGroup/Leetcode/tree/master/October-LeetCoding-Challenge/14-House-Robber-II)
15. [Rotate Array](https://github.com/AlgoStudyGroup/Leetcode/tree/master/October-LeetCoding-Challenge/15-Rotate-Array)
16. [Search a 2D Matrix](https://github.com/AlgoStudyGroup/Leetcode/tree/master/October-LeetCoding-Challenge/16-Search-a-2D-Matrix)
17. [Repeated DNA Sequences](https://github.com/AlgoStudyGroup/Leetcode/tree/master/October-LeetCoding-Challenge/17-Repeated-DNA-Sequences)
18. [Best Time to Buy and Sell Stock IV](https://github.com/AlgoStudyGroup/Leetcode/tree/master/October-LeetCoding-Challenge/18-Best-Time-to-Buy-and-Sell-Stock-IV)
19. [Minimum Domino Rotations For Equal Row](https://github.com/AlgoStudyGroup/Leetcode/tree/master/October-LeetCoding-Challenge/19-Minimum-Domino-Rotations-For-Equal-Row)
20. [Clone Graph](https://github.com/AlgoStudyGroup/Leetcode/tree/master/October-LeetCoding-Challenge/20-Clone-Graph)
21. [Asteroid Collision](https://github.com/AlgoStudyGroup/Leetcode/tree/master/October-LeetCoding-Challenge/21-Asteroid-Collision)
22. [Minimum Depth of Binary Tree](https://github.com/AlgoStudyGroup/Leetcode/tree/master/October-LeetCoding-Challenge/22-Minimum-Depth-of-Binary-Tree)
23. [132 Pattern](https://github.com/AlgoStudyGroup/Leetcode/tree/master/October-LeetCoding-Challenge/23-132-Pattern)
24. [Bag of Tokens](https://github.com/AlgoStudyGroup/Leetcode/tree/master/October-LeetCoding-Challenge/24-Bag-of-Tokens)
25. [Stone Game IV](https://github.com/AlgoStudyGroup/Leetcode/tree/master/October-LeetCoding-Challenge/25-Stone-Game-IV)
26. [Champagne Tower](https://github.com/AlgoStudyGroup/Leetcode/tree/master/October-LeetCoding-Challenge/26-Champagne-Tower)
27. [Linked List Cycle II](https://github.com/AlgoStudyGroup/Leetcode/tree/master/October-LeetCoding-Challenge/27-Linked-List-Cycle-II)
28. [Summary Ranges](https://github.com/AlgoStudyGroup/Leetcode/tree/master/October-LeetCoding-Challenge/28-Summary-Ranges)
29. [Maximum Distance to Closest Person](https://github.com/AlgoStudyGroup/Leetcode/tree/master/October-LeetCoding-Challenge/29-Maximum-Distance-to-Closest-Person)
30. [Number of Longest Increasing Subsequence](https://github.com/AlgoStudyGroup/Leetcode/tree/master/October-LeetCoding-Challenge/30-Number-of-Longest-Increasing-Subsequence)
31. [Recover Binary Search Tree](https://github.com/AlgoStudyGroup/Leetcode/tree/master/October-LeetCoding-Challenge/31-Recover-Binary-Search-Tree)

## September LeetCoding Challenge
Click [here](https://leetcode.com/explore/challenge/card/september-leetcoding-challenge) for problem descriptions.

Solutions in various programming languages are provided. Enjoy it.

1. [Largest Time for Given Digits](https://github.com/AlgoStudyGroup/Leetcode/tree/master/September-LeetCoding-Challenge/01-Largest-Time-for-Given-Digits)
2. [Contains Duplicate III](https://github.com/AlgoStudyGroup/Leetcode/tree/master/September-LeetCoding-Challenge/02-Contains-Duplicate-III)
3. [Repeated Substring Pattern](https://github.com/AlgoStudyGroup/Leetcode/tree/master/September-LeetCoding-Challenge/03-Repeated-Substring-Pattern)
4. [Partition Labels](https://github.com/AlgoStudyGroup/Leetcode/tree/master/September-LeetCoding-Challenge/04-Partition-Labels)
5. [All Elements in Two Binary Search Trees](https://github.com/AlgoStudyGroup/Leetcode/tree/master/September-LeetCoding-Challenge/05-All-Elements-in-Two-Binary-Search-Trees)
6. [Image Overlap](https://github.com/AlgoStudyGroup/Leetcode/tree/master/September-LeetCoding-Challenge/06-Image-Overlap)
7. [Word Pattern](https://github.com/AlgoStudyGroup/Leetcode/tree/master/September-LeetCoding-Challenge/07-Word-Pattern)
8. [Sum of Root To Leaf Binary Numbers](https://github.com/AlgoStudyGroup/Leetcode/tree/master/September-LeetCoding-Challenge/08-Sum-of-Root-To-Leaf-Binary-Numbers)
9. [Compare Version Numbers](https://github.com/AlgoStudyGroup/Leetcode/tree/master/September-LeetCoding-Challenge/09-Compare-Version-Numbers)
10. [Bulls and Cows](https://github.com/AlgoStudyGroup/Leetcode/tree/master/September-LeetCoding-Challenge/10-Bulls-and-Cows)
11. [Maximum Product Subarray](https://github.com/AlgoStudyGroup/Leetcode/tree/master/September-LeetCoding-Challenge/11-Maximum-Product-Subarray)
12. [Combination Sum III](https://github.com/AlgoStudyGroup/Leetcode/tree/master/September-LeetCoding-Challenge/12-Combination-Sum-III)
13. [Insert Interval](https://github.com/AlgoStudyGroup/Leetcode/tree/master/September-LeetCoding-Challenge/13-Insert-Interval)
14. [House Robber](https://github.com/AlgoStudyGroup/Leetcode/tree/master/September-LeetCoding-Challenge/14-House-Robber)
15. [Length of Last Word](https://github.com/AlgoStudyGroup/Leetcode/tree/master/September-LeetCoding-Challenge/15-Length-of-Last-Word)
16. [Maximum XOR of Two Numbers in an Array](https://github.com/AlgoStudyGroup/Leetcode/tree/master/September-LeetCoding-Challenge/16-Maximum-XOR-of-Two-Numbers-in-an-Array)
17. [Robot Bounded In Circle](https://github.com/AlgoStudyGroup/Leetcode/tree/master/September-LeetCoding-Challenge/17-Robot-Bounded-In-Circle)
18. [Best Time to Buy and Sell Stock](https://github.com/AlgoStudyGroup/Leetcode/tree/master/September-LeetCoding-Challenge/18-Best-Time-to-Buy-and-Sell-Stock)
19. [Sequential Digits](https://github.com/AlgoStudyGroup/Leetcode/tree/master/September-LeetCoding-Challenge/19-Sequential-Digits)
23. [Gas Station](https://github.com/AlgoStudyGroup/Leetcode/tree/master/September-LeetCoding-Challenge/23-Gas-Station)
28. [Subarray Product Less Than K](https://github.com/AlgoStudyGroup/Leetcode/tree/master/September-LeetCoding-Challenge/28-Subarray-Product-Less-Than-K)
30. [First Missing Positive](https://github.com/AlgoStudyGroup/Leetcode/tree/master/September-LeetCoding-Challenge/30-First-Missing-Positive)

## August LeetCoding Challenge
Click [here](https://leetcode.com/explore/challenge/card/august-leetcoding-challenge/) for problem descriptions.

Solutions in various programming languages are provided. Enjoy it.

1. [Detect Capital](https://github.com/AlgoStudyGroup/Leetcode/tree/master/August-LeetCoding-Challenge/01-Detect-Capital)
2. [Design HashSet](https://github.com/AlgoStudyGroup/Leetcode/tree/master/August-LeetCoding-Challenge/02-Design-HashSet)
3. [Valid Palindrome](https://github.com/AlgoStudyGroup/Leetcode/tree/master/August-LeetCoding-Challenge/03-Valid-Palindrome)
4. [Power of Four](https://github.com/AlgoStudyGroup/Leetcode/tree/master/August-LeetCoding-Challenge/04-Power-of-Four)
5. [Add and Search Word Data structure design](https://github.com/AlgoStudyGroup/Leetcode/tree/master/August-LeetCoding-Challenge/05-Add-and-Search-Word-Data-structure-design)
6. [Find All Duplicates in an Array](https://github.com/AlgoStudyGroup/Leetcode/tree/master/August-LeetCoding-Challenge/06-Find-All-Duplicates-in-an-Array)
7. [Vertical Order Traversal of a Binary Tree](https://github.com/AlgoStudyGroup/Leetcode/tree/master/August-LeetCoding-Challenge/07-Vertical-Order-Traversal-of-a-Binary-Tree)
8. [Path Sum III](https://github.com/AlgoStudyGroup/Leetcode/tree/master/August-LeetCoding-Challenge/08-Path-Sum-III)
9. [Rotting Oranges](https://github.com/AlgoStudyGroup/Leetcode/tree/master/August-LeetCoding-Challenge/09-Rotting-Oranges)
10. [Excel Sheet Column Number](https://github.com/AlgoStudyGroup/Leetcode/tree/master/August-LeetCoding-Challenge/10-Excel-Sheet-Column-Number)
11. [H-Index](https://github.com/AlgoStudyGroup/Leetcode/tree/master/August-LeetCoding-Challenge/11-H-Index)
12. [Pascal's Triangle II](https://github.com/AlgoStudyGroup/Leetcode/tree/master/August-LeetCoding-Challenge/12-Pascals-Triangle-II)
13. [Iterator for Combination](https://github.com/AlgoStudyGroup/Leetcode/tree/master/August-LeetCoding-Challenge/13-Iterator-for-Combination)
14. [Longest Palindrome](https://github.com/AlgoStudyGroup/Leetcode/tree/master/August-LeetCoding-Challenge/14-Longest-Palindrome)
15. [Non-overlapping Intervals](https://github.com/AlgoStudyGroup/Leetcode/tree/master/August-LeetCoding-Challenge/15-Non-overlapping-Intervals)
16. [Best Time to Buy and Sell Stock III](https://github.com/AlgoStudyGroup/Leetcode/tree/master/August-LeetCoding-Challenge/16-Best-Time-to-Buy-and-Sell-Stock-III)
17. [Distribute Candies to People](https://github.com/AlgoStudyGroup/Leetcode/tree/master/August-LeetCoding-Challenge/17-Distribute-Candies-to-People)
18. [Numbers With Same Consecutive Differences](https://github.com/AlgoStudyGroup/Leetcode/tree/master/August-LeetCoding-Challenge/18-Numbers-With-Same-Consecutive-Differences)
19. [Goat Latin](https://github.com/AlgoStudyGroup/Leetcode/tree/master/August-LeetCoding-Challenge/19-Goat-Latin)
20. [Reorder List](https://github.com/AlgoStudyGroup/Leetcode/tree/master/August-LeetCoding-Challenge/20-Reorder-List)
21. [Sort Array By Parity](https://github.com/AlgoStudyGroup/Leetcode/tree/master/August-LeetCoding-Challenge/21-Sort-Array-By-Parity)
22. [Random Point in Non-overlapping Rectangles](https://github.com/AlgoStudyGroup/Leetcode/tree/master/August-LeetCoding-Challenge/22-Random-Point-in-Non-overlapping-Rectangles)
23. [Stream of Characters](https://github.com/AlgoStudyGroup/Leetcode/tree/master/August-LeetCoding-Challenge/23-Stream-of-Characters)
24. [Sum of Left Leaves](https://github.com/AlgoStudyGroup/Leetcode/tree/master/August-LeetCoding-Challenge/24-Sum-of-Left-Leaves)
25. [Minimum Cost For Tickets](https://github.com/AlgoStudyGroup/Leetcode/tree/master/August-LeetCoding-Challenge/25-Minimum-Cost-For-Tickets)
26. [Fizz Buzz](https://github.com/AlgoStudyGroup/Leetcode/tree/master/August-LeetCoding-Challenge/26-Fizz-Buzz)
27. [Find Right Interval](https://github.com/AlgoStudyGroup/Leetcode/tree/master/August-LeetCoding-Challenge/27-Find-Right-Interval)
28. [Implement Rand10() Using Rand7()](https://github.com/AlgoStudyGroup/Leetcode/tree/master/August-LeetCoding-Challenge/28-Implement-Rand10()-Using-Rand7())
29. [Pancake Sorting](https://github.com/AlgoStudyGroup/Leetcode/tree/master/August-LeetCoding-Challenge/29-Pancake-Sorting)
30. [Largest Component Size by Common Factor](https://github.com/AlgoStudyGroup/Leetcode/tree/master/August-LeetCoding-Challenge/30-Largest-Component-Size-by-Common-Factor)
31. [Delete Node in a BST](https://github.com/AlgoStudyGroup/Leetcode/tree/master/August-LeetCoding-Challenge/31-Delete-Node-in-a-BST)

## July LeetCoding Challenge
Click [here](https://leetcode.com/explore/featured/card/july-leetcoding-challenge/) for problem descriptions.

Solutions in various programming languages are provided. Enjoy it.

1. [Arranging Coins](https://github.com/AlgoStudyGroup/Leetcode/tree/master/July-LeetCoding-Challenge/01-Arranging-Coins): Maths
2. [Binary Tree Level Order Traversal II](https://github.com/AlgoStudyGroup/Leetcode/tree/master/July-LeetCoding-Challenge/02-Binary-Tree-Level-Order-Traversal-II): DFS
3. [Prison Cells After N Days](https://github.com/AlgoStudyGroup/Leetcode/tree/master/July-LeetCoding-Challenge/03-Prison-Cells-After-N-Days): Maths
4. [Ugly Number II](https://github.com/AlgoStudyGroup/Leetcode/tree/master/July-LeetCoding-Challenge/04-Ugly-Number-II): DP
5. [Hamming Distance](https://github.com/AlgoStudyGroup/Leetcode/tree/master/July-LeetCoding-Challenge/05-Hamming-Distance): Bitwise Manipulation
6. [Plus One](https://github.com/AlgoStudyGroup/Leetcode/tree/master/July-LeetCoding-Challenge/06-Plus-One): Maths
7. [Island Perimeter](https://github.com/AlgoStudyGroup/Leetcode/tree/master/July-LeetCoding-Challenge/07-Island-Perimeter): BFS
8. [3Sum](https://github.com/AlgoStudyGroup/Leetcode/tree/master/July-LeetCoding-Challenge/08-3Sum): Two pointers
9. [Maximum Width of Binary Tree](https://github.com/AlgoStudyGroup/Leetcode/tree/master/July-LeetCoding-Challenge/09-Maximum-Width-of-Binary-Tree): DFS
10. [Flatten a Multilevel Doubly Linked List](https://github.com/AlgoStudyGroup/Leetcode/tree/master/July-LeetCoding-Challenge/10-Flatten-a-Multilevel-Doubly-Linked-List): Queue
11. [Subsets](https://github.com/AlgoStudyGroup/Leetcode/tree/master/July-LeetCoding-Challenge/11-Subsets): DP
12. [Reverse Bits](https://github.com/AlgoStudyGroup/Leetcode/tree/master/July-LeetCoding-Challenge/12-Reverse-Bits): Bitwise
13. [Same Tree](https://github.com/AlgoStudyGroup/Leetcode/tree/master/July-LeetCoding-Challenge/13-Same-Tree): DFS
14. [Angle Between Hands of a Clock](https://github.com/AlgoStudyGroup/Leetcode/tree/master/July-LeetCoding-Challenge/14-Angle-Between-Hands-of-a-Clock): Math
15. [Reverse Words in a String](https://github.com/AlgoStudyGroup/Leetcode/tree/master/July-LeetCoding-Challenge/15-Reverse-Words-in-a-String): Pointer
16. [Pow(x,n)](https://github.com/AlgoStudyGroup/Leetcode/tree/master/July-LeetCoding-Challenge/16-Pow(x,n)): Recursion
17. [Top K Frequent Elements](https://github.com/AlgoStudyGroup/Leetcode/tree/master/July-LeetCoding-Challenge/17-Top-K-Frequent-Elements): Bucket
18. [Course Schedule II](https://github.com/AlgoStudyGroup/Leetcode/tree/master/July-LeetCoding-Challenge/18-Course-Schedule-II): BFS
19. [Add Binary](https://github.com/AlgoStudyGroup/Leetcode/tree/master/July-LeetCoding-Challenge/19-Add-Binary)
20. [Remove Linked List Elements](https://github.com/AlgoStudyGroup/Leetcode/tree/master/July-LeetCoding-Challenge/20-Remove-Linked-List-Elements)
21. [Word Search](https://github.com/AlgoStudyGroup/Leetcode/tree/master/July-LeetCoding-Challenge/21-Word-Search)
22. [Binary Tree Zigzag Level Order Traversal](https://github.com/AlgoStudyGroup/Leetcode/tree/master/July-LeetCoding-Challenge/22-Binary-Tree-Zigzag-Level-Order-Traversal)
23. [Single Number III](https://github.com/AlgoStudyGroup/Leetcode/tree/master/July-LeetCoding-Challenge/23-Single-Number-III)
24. [All Paths From Source to Target](https://github.com/AlgoStudyGroup/Leetcode/tree/master/July-LeetCoding-Challenge/24-All-Paths-From-Source-to-Target)
25. [Find Minimum in Rotated Sorted Array II](https://github.com/AlgoStudyGroup/Leetcode/tree/master/July-LeetCoding-Challenge/25-Find-Minimum-in-Rotated-Sorted-Array-II)
26. [Add Digits](https://github.com/AlgoStudyGroup/Leetcode/tree/master/July-LeetCoding-Challenge/26-Add-Digits)
27. [Construct Binary Tree from Inorder and Postorder Traversal](https://github.com/AlgoStudyGroup/Leetcode/tree/master/July-LeetCoding-Challenge/27-Construct-Binary-Tree-from-Inorder-and-Postorder-Traversal)
28. [Task Scheduler](https://github.com/AlgoStudyGroup/Leetcode/tree/master/July-LeetCoding-Challenge/28-Task-Scheduler)
29. [Best Time to Buy and Sell Stock with Cooldown](https://github.com/AlgoStudyGroup/Leetcode/tree/master/July-LeetCoding-Challenge/29-Best-Time-to-Buy-and-Sell-Stock-with-Cooldown): State machine
30. [Word Break II](https://github.com/AlgoStudyGroup/Leetcode/tree/master/July-LeetCoding-Challenge/30-Word-Break-II)
31. [Climbing Stairs](https://github.com/AlgoStudyGroup/Leetcode/tree/master/July-LeetCoding-Challenge/31-Climbing-Stairs): DP

## June LeetCoding Challenge
Click [here](https://leetcode.com/explore/challenge/card/june-leetcoding-challenge/) for problem descriptions.

Solutions in various programming languages are provided. Enjoy it.

1. [Invert Binary Tree](https://github.com/AlgoStudyGroup/Leetcode/tree/master/June-LeetCoding-Challenge/01-Invert-Binary-Tree): Tree Traversal
2. [Delete Node in a Linked List](https://github.com/AlgoStudyGroup/Leetcode/tree/master/June-LeetCoding-Challenge/02-Delete-Node-In-A-Linked-List): Linked List
3. [Two City Scheduling](https://github.com/AlgoStudyGroup/Leetcode/tree/master/June-LeetCoding-Challenge/03-Two-City-Scheduling): DP
4. [Reverse String](https://github.com/AlgoStudyGroup/Leetcode/tree/master/June-LeetCoding-Challenge/04-Reverse-String): String
5. [Random Pick With Weight](https://github.com/AlgoStudyGroup/Leetcode/tree/master/June-LeetCoding-Challenge/05-Random-Pick-With-Weight): Binary Search + Probability
6. [Queue Reconstruction by Height](https://github.com/AlgoStudyGroup/Leetcode/tree/master/June-LeetCoding-Challenge/06-Queue-Reconstruction-By-Height): Greedy
7. [Coin Change 2](https://github.com/AlgoStudyGroup/Leetcode/tree/master/June-LeetCoding-Challenge/07-Coin-Change-2): DP
8. [Power of Two](https://github.com/AlgoStudyGroup/Leetcode/tree/master/June-LeetCoding-Challenge/08-Power-Of-Two): Bitwise manipulation
9. [Is Subsequence](https://github.com/AlgoStudyGroup/Leetcode/blob/master/June-LeetCoding-Challenge/09-Is-Subsequence): Two pointers / DP
10. [Search Insert Position](https://github.com/AlgoStudyGroup/Leetcode/tree/master/June-LeetCoding-Challenge/10-Search-Insert-Position): Binary Search
11. [Sort Colors](https://github.com/AlgoStudyGroup/Leetcode/tree/master/June-LeetCoding-Challenge/11-Sort-Colors): Two Pointers
12. [Insert Delete GetRandom](https://github.com/AlgoStudyGroup/Leetcode/tree/master/June-LeetCoding-Challenge/12-Insert-Delete-GetRandom): Hash Table
13. [Largest Divisible Subset](https://github.com/AlgoStudyGroup/Leetcode/tree/master/June-LeetCoding-Challenge/13-Largest-Divisible-Subset): DP
14. [Cheapest Flights Within K Stops](https://github.com/AlgoStudyGroup/Leetcode/tree/master/June-LeetCoding-Challenge/14-Cheapest-Flights-Within-K-Stops): DP
15. [Search in a Binary Search Tree](https://github.com/AlgoStudyGroup/Leetcode/tree/master/June-LeetCoding-Challenge/15-Search-In-A-Binary-Search-Tree): Recursive
16. [Validate IP Address](https://github.com/AlgoStudyGroup/Leetcode/tree/master/June-LeetCoding-Challenge/16-Validate-IP-Address): String
17. [Surrounded Regions](https://github.com/AlgoStudyGroup/Leetcode/tree/master/June-LeetCoding-Challenge/17-Surrounded-Regions): BFS
18. [H Index II](https://github.com/AlgoStudyGroup/Leetcode/tree/master/June-LeetCoding-Challenge/18-H-Index-II): Binary Search
19. [Longest Duplicate Substring]():  
20. [Permutation Sequence](https://github.com/AlgoStudyGroup/Leetcode/tree/master/June-LeetCoding-Challenge/20-Permutation-Sequence): Maths
21. [Dungeon Game](https://github.com/AlgoStudyGroup/Leetcode/tree/master/June-LeetCoding-Challenge/21-Dungeon-Game): DP
22. [Single Number II](https://github.com/AlgoStudyGroup/Leetcode/tree/master/June-LeetCoding-Challenge/22-Single-Number-II): Bitwise Manipulation
23. [Count Complete Tree Nodes](https://github.com/AlgoStudyGroup/Leetcode/tree/master/June-LeetCoding-Challenge/23-Count-Complete-Tree-Nodes): Tree Traversal
24. [Unique Binary Search Trees](https://github.com/AlgoStudyGroup/Leetcode/tree/master/June-LeetCoding-Challenge/24-Unique-Binary-Search-Trees): DP
25. [Find the Duplicate Number](https://github.com/AlgoStudyGroup/Leetcode/tree/master/June-LeetCoding-Challenge/25-Find-the-Duplicate-Number): Cycle Detect
26. [Sum Root To Leaf Numbers](https://github.com/AlgoStudyGroup/Leetcode/tree/master/June-LeetCoding-Challenge/26-Sum-Root-to-Leaf-Numbers): DFS
27. [Perfect Squares](https://github.com/AlgoStudyGroup/Leetcode/tree/master/June-LeetCoding-Challenge/27-Perfect-Squares): DP
28. [Reconstruct Itinerary](https://github.com/AlgoStudyGroup/Leetcode/tree/master/June-LeetCoding-Challenge/28-Reconstruct-Itinerary): DFS
29. [Unique Paths](https://github.com/AlgoStudyGroup/Leetcode/tree/master/June-LeetCoding-Challenge/29-Unique-Paths): DP
30. [Word Search](https://github.com/AlgoStudyGroup/Leetcode/tree/master/June-LeetCoding-Challenge/30-Word-Search-II): Trie + DFS

## May LeetCoding Challenge

Click [here](https://leetcode.com/explore/featured/card/may-leetcoding-challenge/) for problem descriptions.

Solutions in various programming languages are provided. Enjoy it.

1. [First Bad String](https://github.com/AlgoStudyGroup/Leetcode/tree/master/May-LeetCoding-Challenge/01-First-Bad-Version): Binary search.
2. [Jewels and Stones](https://github.com/AlgoStudyGroup/Leetcode/tree/master/May-LeetCoding-Challenge/02-Jewels-And-Stones): Hash Table
3. [Ransom Note](https://github.com/AlgoStudyGroup/Leetcode/tree/master/May-LeetCoding-Challenge/03-Ransom-Note): Hash Table
4. [Number Complement](https://github.com/AlgoStudyGroup/Leetcode/tree/master/May-LeetCoding-Challenge/04-Number-Complement): Bitwise Manipulation
5. [First Unique Character In a String](https://github.com/AlgoStudyGroup/Leetcode/tree/master/May-LeetCoding-Challenge/05-First-Unique-Character-In-A-String): Hash Table
6. [Majority Element](https://github.com/AlgoStudyGroup/Leetcode/tree/master/May-LeetCoding-Challenge/06-Majority-Element): Ad hoc
7. [Cousins in Binary Tree](https://github.com/AlgoStudyGroup/Leetcode/tree/master/May-LeetCoding-Challenge/07-Cousins-In-Binary-Tree): BFS / 
Recursion 
8. [Check if it is straight line](https://github.com/AlgoStudyGroup/Leetcode/tree/master/May-LeetCoding-Challenge/08-Check-If-It-Is-A-Straight-Line): Cross Product
9. [Valid Perfect Square](https://github.com/AlgoStudyGroup/Leetcode/tree/master/May-LeetCoding-Challenge/09-Valid-Perfect-Square): Math
10. [Find the Town Judge](https://github.com/AlgoStudyGroup/Leetcode/tree/master/May-LeetCoding-Challenge/10-Find-The-Town-Judge): Graph Theory 
11. [Flood Fill](https://github.com/AlgoStudyGroup/Leetcode/tree/master/May-LeetCoding-Challenge/11-Flood-Fill): BFS
12. [Single Element In a Sorted Array](https://github.com/AlgoStudyGroup/Leetcode/tree/master/May-LeetCoding-Challenge/12-Single-Element-In-A-Sorted-Array): Binary Search
13. [Remove K Digits](https://github.com/AlgoStudyGroup/Leetcode/tree/master/May-LeetCoding-Challenge/13-Remove-K-Digits): Greedy
14. [Implement Trie](https://github.com/AlgoStudyGroup/Leetcode/tree/master/May-LeetCoding-Challenge/14-Implement-Trie): Trie
15. [Maximum Sum Circular Subarray](https://github.com/AlgoStudyGroup/Leetcode/tree/master/May-LeetCoding-Challenge/15-Maximum-Sum-Circular-Subarray): DP
16. [Odd Even Linked List](https://github.com/AlgoStudyGroup/Leetcode/tree/master/May-LeetCoding-Challenge/16-Odd-Even-Linked-List): Linked List
17. [Find All Anagrams in a String](https://github.com/AlgoStudyGroup/Leetcode/tree/master/May-LeetCoding-Challenge/17-Find-All-Anagrams-In-A-String): Sliding window + Hash Table
18. [Permutation In String](https://github.com/AlgoStudyGroup/Leetcode/tree/master/May-LeetCoding-Challenge/18-Permutation-In-String): Sliding window + Hash Table
19. [Online Stock Span](https://github.com/AlgoStudyGroup/Leetcode/tree/master/May-LeetCoding-Challenge/19-Online-Stock-Span): DP
20. [Kth-Smallest-Element-In-A-BST](https://github.com/AlgoStudyGroup/Leetcode/tree/master/May-LeetCoding-Challenge/20-Kth-Smallest-Element-In-A-BST): BST
21. [Count Square Submatrices with All Ones](https://github.com/AlgoStudyGroup/Leetcode/tree/master/May-LeetCoding-Challenge/21-Count-Square-Submatrices-With-All-Ones): DP
22. [Sort Characters By Frequency](https://github.com/AlgoStudyGroup/Leetcode/tree/master/May-LeetCoding-Challenge/22-Sort-Characters-By-Frequency): Hash Table
23. [Interval List Intersections](https://github.com/AlgoStudyGroup/Leetcode/tree/master/May-LeetCoding-Challenge/23-Interval-List-Intersections): Two Pointers
24. [Construct Binary Search Tree from Preorder Traversal](https://github.com/AlgoStudyGroup/Leetcode/tree/master/May-LeetCoding-Challenge/24-Construct-Binary-Search-Tree-From-Preorder-Traversal): Binary Search Tree
25. [Uncrossed Lines](https://github.com/AlgoStudyGroup/Leetcode/tree/master/May-LeetCoding-Challenge/25-Uncrossed-Lines): DP
26. [Contiguous Array](https://github.com/AlgoStudyGroup/Leetcode/tree/master/May-LeetCoding-Challenge/26-Contiguous-Array): Hash Table
27. [Possible Bipartition](https://github.com/AlgoStudyGroup/Leetcode/tree/master/May-LeetCoding-Challenge/27-Possible-Bipartition): Bipartite Graph
28. [Counting Bits](https://github.com/AlgoStudyGroup/Leetcode/tree/master/May-LeetCoding-Challenge/28-Counting-Bits): Math
29.	[Course Schedule](https://github.com/AlgoStudyGroup/Leetcode/tree/master/May-LeetCoding-Challenge/29-Course-Schedule): Topological Sort
30. [K Closest Points to Origin](https://github.com/AlgoStudyGroup/Leetcode/tree/master/May-LeetCoding-Challenge/30-K-Closest-Points-To-Origin): Priority_queue, Sort
31. [Edit Distance](https://github.com/AlgoStudyGroup/Leetcode/tree/master/May-LeetCoding-Challenge/31-Edit-Distance): DP

## 30-Day (April) LeetCoding Challenge

Click [here](https://leetcode.com/explore/challenge/card/30-day-leetcoding-challenge/) for problem descriptions.

1. [Single Number](https://github.com/AlgoStudyGroup/Leetcode/tree/master/30-Day-Leetcoding-Challenge/01-Single-Number): Bitwise Manipulation
2. [Happy Number](https://github.com/AlgoStudyGroup/Leetcode/blob/master/30-Day-Leetcoding-Challenge/02-Happy-Number): Implementation
3. [Maximum Subarray](https://github.com/AlgoStudyGroup/Leetcode/blob/master/30-Day-Leetcoding-Challenge/03-Maximum-Subarray): DP
4. [Move Zeros](https://github.com/AlgoStudyGroup/Leetcode/blob/master/30-Day-Leetcoding-Challenge/04-Move-Zeros): Two pointers
5. [Best Time to Buy and Sell Stock II](https://github.com/AlgoStudyGroup/Leetcode/tree/master/30-Day-Leetcoding-Challenge/05-Best-Time-To-Buy-And-Sell-Stock-II): Greedy
6. [Group Anagrams](https://github.com/AlgoStudyGroup/Leetcode/tree/master/30-Day-Leetcoding-Challenge/06-Group-Anagrams): Hash Table

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