🚀 LeetCode DSA Solutions Repository 🚀

Welcome to my LeetCode DSA Solutions repository! This space is dedicated to solving and documenting solutions to LeetCode problems focused on Data Structures and Algorithms (DSA). Whether you're preparing for technical interviews 💼, improving your problem-solving skills 🧠, or just exploring the beauty of algorithms, this repo is here to help.

📚 About This Repository

This repository contains Python 🐍 solutions to various LeetCode problems categorized by data structures and algorithms. Each solution is carefully written to be clean, efficient, and well-documented, making it easy for learners to understand and adapt.

🎯 Goals:

• Solve a wide range of DSA problems to strengthen algorithmic thinking.
• Provide clear explanations and optimized code for each problem.
• Create a structured resource for interview preparation and learning.

🏷️ Categories

Order	Description
🧱 Arrays	The most fundamental data structure. Solving array problems helps build a strong foundation in algorithms.
↔️ Two Pointers	Builds on arrays and introduces efficient traversal techniques for solving problems like two-sum and subarray manipulation.
🖇️ Sliding Window	Extends two pointers to solve subarray/substring problems, often used in problems involving contiguous sequences.
🐢🐇 Fast & Slow Pointers	Focuses on linked lists and cycle detection, building on pointer manipulation techniques.
🔍 Modified Binary Search	A foundational algorithm for searching in sorted data, often extended to solve more complex variations.
📅 Merge Intervals	Introduces interval-based problems, which are common in real-world applications like scheduling and resource allocation.
🔄 K-way Merge	Extends merging concepts to handle multiple sorted inputs, such as merging k sorted lists or finding the smallest range.
⚖️ 2 Heaps	Useful for solving problems involving medians or dynamic sets, leveraging min-heaps and max-heaps.
🔝 Top K Elements	Builds on heaps and sorting for finding top elements, such as the kth largest element or k closest points.
↪️🔄 Backtracking	Introduces recursion and combinatorial problem-solving, commonly used in problems involving subsets, permutations, and combinations.
💡 Dynamic Programming (DP)	A powerful technique for optimization and counting problems, using memoization or tabulation to solve subproblems efficiently.
🌳🌍 Graph Traversal	Essential for solving problems involving networks, paths, or connectivity, using algorithms like DFS and BFS.
🔀 Topological Sorting	Builds on graph traversal for dependency resolution, commonly used in scheduling and ordering problems.
🌲 Tree BFS/DFS	Fundamental for solving tree-based problems, including level-order traversal, path sums, and tree serialization.
🔗 In-place Traversal of Linked List	Advanced linked list manipulation without extra space, focusing on efficient pointer reassignment.

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📂 Repository Structure

Each problem will have its own folder with the following structure:

/problems
  ├── {Problem_Name}/
  │     ├── solution.py       # Python solution file
  │     ├── README.md         # Problem description, approach, and complexity analysis
  │     └── test_cases.py     # Sample test cases (optional)

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🛠️ How to Use This Repository

1. Clone the Repository:

   git clone https://github.com/onyxwizard/leetcode.git
   cd leetcode

2. Explore Solutions:

   Navigate through the /problems directory to find solutions by category or difficulty.
   

3. Run the Code:

   Open the solution.py file in your favorite Python IDE or run it directly:
   

4. Contribute:

   Contributions are welcome! If you'd like to add a new solution or improve an existing one, feel free to open a pull request.

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🌟 Arrays Problems

Below is the list of problems under the Arrays pattern:

Problem	Difficulty	Acceptance Rate	Progress	Link	Solution
448. Find All Numbers Disappeared in an Array	Easy	62.1%	🟩	LeetCode	📝
136. Single Number	Easy	75.5%	🟩	LeetCode	📝
268. Missing Number	Easy	69.6%	🟩	LeetCode	📝
217. Contains Duplicate	Easy	62.9%	🟩	LeetCode	📝
128. Longest Consecutive Sequence	Medium	47.1%	🟩	LeetCode	📝
581. Shortest Unsorted Continuous Subarray	Medium	37.3%	🟩	LeetCode	📝
73. Set Matrix Zeroes	Medium	59.2%	🟩	LeetCode	📝
457. Circular Array Loop	Medium	35.3%	⬜	LeetCode
792. Number of Matching Subsequences	Medium	50.7%	⬜	LeetCode
238. Product of Array Except Self	Medium	67.5%	⬜	LeetCode
79. Word Search	Medium	44.8%	⬜	LeetCode
48. Rotate Image	Medium	77.4%	⬜	LeetCode
54. Spiral Matrix	Medium	53.2%	⬜	LeetCode
442. Find All Duplicates in an Array	Medium	76.3%	⬜	LeetCode
287. Find the Duplicate Number	Medium	62.5%	🟩	LeetCode	📝
41. First Missing Positive	Hard	40.8%	⬜	LeetCode

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🌟 Two Pointers Problems

Below is the list of problems under the Two Pointers pattern:

Problem	Difficulty	Acceptance Rate	Progress	Link	Solution
1. Two Sum	Easy	55.3%	🟩	LeetCode	📝
844. Backspace String Compare	Easy	49.4%	🟩	LeetCode	📝
83. Remove Duplicates from Sorted List	Easy	54.5%	⬜	LeetCode
977. Squares of a Sorted Array	Easy	73.1%	🟩	LeetCode	📝
259. 3Sum Smaller	Medium	50.9%	⬜	LeetCode
713. Subarray Product Less Than K	Medium	52.5%	🟩	LeetCode	📝
11. Container With Most Water	Medium	57.4%	⬜	LeetCode
75. Sort Colors	Medium	66.6%	⬜	LeetCode
15. 3Sum	Medium	36.6%	⬜	LeetCode
16. 3Sum Closest	Medium	46.7%	⬜	LeetCode
42. Trapping Rain Water	Hard	64.5%	⬜	LeetCode
76. Minimum Window Substring	Hard	44.9%	⬜	LeetCode

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🌟 Sliding Window Problems

Below is the list of problems under the Sliding Window pattern:

Problem	Difficulty	Acceptance Rate	Progress	Link	Solution
3. Longest Substring Without Repeating Characters	Medium	36.5%	⬜	LeetCode
424. Longest Repeating Character Replacement	Medium	56.6%	⬜	LeetCode
904. Fruit Into Baskets	Medium	45.8%	⬜	LeetCode
209. Minimum Size Subarray Sum	Medium	48.9%	⬜	LeetCode
340. Longest Substring with At Most K Distinct Characters	Medium	49.4%	⬜	LeetCode
567. Permutation in String	Medium	46.9%	⬜	LeetCode
76. Minimum Window Substring	Hard	44.9%	⬜	LeetCode
828. Count Unique Characters of All Substrings of a Given String	Hard	52.7%	⬜	LeetCode
239. Sliding Window Maximum	Hard	47.3%	⬜	LeetCode
995. Minimum Number of K Consecutive Bit Flips	Hard	62.1%	⬜	LeetCode
30. Substring with Concatenation of All Words	Hard	32.8%	⬜	LeetCode

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🌟 Fast & Slow Pointers Problems

Below is the list of problems under the Fast & Slow Pointers pattern:

Problem Number	Title	Difficulty	Acceptance Rate	Status	Platform	Solution
234	Palindrome Linked List	Easy	55.4%	⬜	LeetCode
203	Remove Linked List Elements	Easy	51.4%	⬜	LeetCode
876	Middle of the Linked List	Easy	80.3%	⬜	LeetCode
141	Linked List Cycle	Easy	52.1%	⬜	LeetCode
83	Remove Duplicates from Sorted List	Easy	54.5%	⬜	LeetCode
2	Add Two Numbers	Medium	45.7%	⬜	LeetCode
142	Linked List Cycle II	Medium	54.3%	⬜	LeetCode
143	Reorder List	Medium	61.9%	⬜	LeetCode
19	Remove Nth Node From End of List	Medium	48.4%	⬜	LeetCode
148	Sort List	Medium	61.1%	⬜	LeetCode

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🌟 Modified Binary Search Problems

Below is the list of problems under the Modified Binary Search pattern:

Problem Number	Title	Difficulty	Acceptance Rate	Status	Platform	Solution
704	Binary Search	Easy	59.3%	⬜	LeetCode
744	Find Smallest Letter Greater Than Target	Easy	53.7%	⬜	LeetCode
33	Search in Rotated Sorted Array	Medium	42.5%	⬜	LeetCode
162	Find Peak Element	Medium	46.4%	⬜	LeetCode
74	Search a 2D Matrix	Medium	51.9%	⬜	LeetCode
81	Search in Rotated Sorted Array II	Medium	38.7%	⬜	LeetCode
852	Peak Index in a Mountain Array	Medium	67.7%	⬜	LeetCode
153	Find Minimum in Rotated Sorted Array	Medium	52.3%	⬜	LeetCode
327	Count of Range Sum	Hard	36.7%	⬜	LeetCode

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🌟 Merge Intervals Problems

Below is the list of problems under the Merge Intervals pattern:

Problem Number	Title	Difficulty	Acceptance Rate	Status	Platform	Solution
252	Meeting Rooms	Easy	58.8%	⬜	LeetCode
435	Non-overlapping Intervals	Medium	55.1%	⬜	LeetCode
452	Minimum Number of Arrows to Burst Balloons	Medium	60.1%	⬜	LeetCode
56	Merge Intervals	Medium	49.0%	⬜	LeetCode
57	Insert Interval	Medium	43.1%	⬜	LeetCode
621	Task Scheduler	Medium	61.1%	⬜	LeetCode
986	Interval List Intersections	Medium	72.5%	⬜	LeetCode
253	Meeting Rooms II	Medium	52.0%	⬜	LeetCode

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🌟 K-Way Merge Problems

Below is the list of problems under the K-Way Merge pattern:

Problem Number	Title	Difficulty	Acceptance Rate	Status	Platform	Solution
21	Merge Two Sorted Lists	Easy	66.5%	⬜	LeetCode
373	Find K Pairs with Smallest Sums	Medium	40.5%	⬜	LeetCode
378	Kth Smallest Element in a Sorted Matrix	Medium	63.3%	⬜	LeetCode
23	Merge k Sorted Lists	Hard	56.1%	⬜	LeetCode
632	Smallest Range Covering Elements from K Lists	Hard	69.7%	⬜	LeetCode

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🌟 2 Heaps Problems

Below is the list of problems under the 2 Heaps pattern:

Problem Number	Title	Difficulty	Acceptance Rate	Status	Platform	Solution
295	Find Median from Data Stream	Hard	53.1%	⬜	LeetCode
480	Sliding Window Median	Hard	38.6%	⬜	LeetCode
502	IPO	Hard	53.0%	⬜	LeetCode

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📈 Progress Tracker

Pattern	Progress
Arrays	🟩⬜⬜⬜⬜
Two Pointers	⬜⬜⬜⬜⬜
Sliding Window	⬜⬜⬜⬜⬜
Fast & Slow Pointers	⬜⬜⬜⬜⬜
Modified Binary Search	⬜⬜⬜⬜⬜
Merge Intervals	⬜⬜⬜⬜⬜
K-way Merge	⬜⬜⬜⬜⬜
2 Heaps	⬜⬜⬜⬜⬜
Top K Elements	⬜⬜⬜⬜⬜
Backtracking	⬜⬜⬜⬜⬜
Dynamic Programming	⬜⬜⬜⬜⬜
Graph Traversal	⬜⬜⬜⬜⬜
Topological Sorting	⬜⬜⬜⬜⬜
Tree BFS	⬜⬜⬜⬜⬜
Tree DFS	⬜⬜⬜⬜⬜
In-place Traversal of LL	⬜⬜⬜⬜⬜

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📜 License

This repository is licensed under the MIT License. Feel free to use, modify, and distribute the code as per the license terms. Attribution is appreciated but not mandatory.

For more details, see the LICENSE file.

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🌟 Acknowledgments

• Special thanks to LeetCode for providing an incredible platform to practice DSA problems.
• Some solutions may have been inspired or refined with the help of AI tools like ChatGPT or GitHub Copilot. e