Data Structures and Algorithms - LeetCode Solutions

This repository contains solutions to various LeetCode problems, primarily implemented in C++ with some Java solutions. The problems cover a wide range of data structures and algorithms topics, perfect for interview preparation and competitive programming practice.

📊 Statistics

• Total Problems: 68
• Easy: 33 problems
• Medium: 32 problems
• Hard: 3 problems

📚 Problem List

Easy Problems (33)

#	Problem	Solution	Difficulty
1	Two Sum	C++	Easy
20	Valid Parentheses	C++	Easy
26	Remove Duplicates from Sorted Array	C++	Easy
35	Search Insert Position	C++	Easy
69	Sqrt(x)	C++	Easy
70	Climbing Stairs	Java	Easy
88	Merge Sorted Array	C++	Easy
118	Pascal's Triangle	C++	Easy
119	Pascal's Triangle II	C++	Easy
121	Best Time to Buy and Sell Stock	C++	Easy
136	Single Number	C++	Easy
169	Majority Element	C++	Easy
231	Power of Two	C++	Easy
242	Valid Anagram	C++	Easy
283	Move Zeroes	C++	Easy
392	Is Subsequence	C++	Easy
485	Max Consecutive Ones	C++	Easy
496	Next Greater Element I	C++	Easy
792	Binary Search	-	Easy
1013	Fibonacci Number	C++	Easy
1018	Largest Perimeter Triangle	C++	Easy
1353	Find Resultant Array After Removing Anagrams	C++	Easy
1421	Find Numbers with Even Number of Digits	C++	Easy
1476	Count Negative Numbers in a Sorted Matrix	C++	Easy
1642	Water Bottles	C++	Easy
1769	Get Maximum in Generated Array	C++	Easy
1791	Richest Customer Wealth	C++	Easy
1878	Check if Array Is Sorted and Rotated	C++	Easy
1950	Sign of the Product of an Array	C++	Easy
2106	Find Greatest Common Divisor of Array	C++	Easy
2132	Convert 1D Array Into 2D Array	C++	Easy
4039	Compute Decimal Representation	C++	Easy
4068	Sum of Elements With Frequency Divisible by K	C++	Easy

Medium Problems (32)

#	Problem	Solution	Difficulty
6	Zigzag Conversion	C++	Medium
7	Reverse Integer	C++	Medium
11	Container With Most Water	C++	Medium
18	4Sum	C++	Medium
31	Next Permutation	C++	Medium
33	Search in Rotated Sorted Array	C++	Medium
34	Find First and Last Position of Element in Sorted Array	C++	Medium
48	Rotate Image	C++	Medium
53	Maximum Subarray	C++	Medium
54	Spiral Matrix	C++	Medium
56	Merge Intervals	C++	Medium
73	Set Matrix Zeroes	C++	Medium
74	Search a 2D Matrix	C++	Medium
75	Sort Colors	C++	Medium
128	Longest Consecutive Sequence	C++	Medium
134	Gas Station	C++	Medium
152	Maximum Product Subarray	C++	Medium
155	Min Stack	C++	Medium
189	Rotate Array	C++	Medium
229	Majority Element II	C++	Medium
240	Search a 2D Matrix II	C++	Medium
287	Find the Duplicate Number	C++	Medium
417	Pacific Atlantic Water Flow	C++	Medium
503	Next Greater Element II	C++	Medium
540	Single Element in a Sorted Array	C++	Medium
556	Next Greater Element III	C++	Medium
948	Sort an Array	C++	Medium
2271	Rearrange Array Elements by Sign	C++	Medium
2324	Find Triangular Sum of an Array	C++	Medium
3336	Water Bottles II	C++	Medium
3383	Taking Maximum Energy From the Mystic Dungeon	C++	Medium
4055	Longest Balanced Substring I	C++	Medium

Hard Problems (3)

#	Problem	Solution	Difficulty
315	Count of Smaller Numbers After Self	C++	Hard
407	Trapping Rain Water II	C++	Hard
493	Reverse Pairs	C++	Hard

🚀 Topics Covered

• Arrays: Two Sum, Move Zeroes, Rotate Array, Majority Element, Remove Duplicates
• Dynamic Programming: Climbing Stairs, Fibonacci Number, Maximum Subarray, Maximum Product Subarray
• Matrix Operations: Rotate Image, Spiral Matrix, Set Matrix Zeroes, Search 2D Matrix
• Searching: Binary Search, Search in Rotated Sorted Array, Find First and Last Position
• Sorting: Sort Colors, Sort an Array, Merge Intervals
• Stack: Valid Parentheses, Min Stack, Next Greater Element I/II/III
• String Manipulation: Zigzag Conversion, Valid Anagram, Is Subsequence
• Math: Reverse Integer, Sqrt(x), Pascal's Triangle, Power of Two
• Greedy: Best Time to Buy and Sell Stock, Container With Most Water, Gas Station
• Hashing: Two Sum, Single Number, Majority Element
• Two Pointers: Move Zeroes, Sort Colors, Merge Sorted Array
• Divide & Conquer: Reverse Pairs, Count of Smaller Numbers After Self
• Bit Manipulation: Single Number, Power of Two, Sign of Product
• Graph/DFS/BFS: Pacific Atlantic Water Flow, Trapping Rain Water II

📝 Repository Structure

Each problem is organized in its own directory with the following structure:

problem-number-problem-name/
├── README.md           # Problem description from LeetCode
└── problem-name.cpp    # C++ solution

💡 How to Use This Repository

1. Browse Problems: Navigate through the categorized problem list above
2. Study Solutions: Each problem folder contains:
   • README.md: Original problem description from LeetCode
   • Solution file (.cpp or .java): Commented code with explanations
3. Practice: Try solving the problems yourself before looking at the solutions
4. Learn: Study the approaches, time/space complexity, and patterns used

🤝 Contributing

Contributions are welcome! If you'd like to add more solutions or improve existing ones:

1. Fork the repository
2. Create a new branch (git checkout -b feature/new-solution)
3. Add your solution following the existing structure
4. Commit your changes (git commit -m 'Add solution for Problem XYZ')
5. Push to the branch (git push origin feature/new-solution)
6. Open a Pull Request

📝 Solution Guidelines

• Use clear and descriptive variable names
• Add comments explaining complex logic
• Include time and space complexity analysis where applicable
• Follow consistent code formatting

🔗 Connect

Feel free to explore the solutions and learn from them. If you have any suggestions or improvements, contributions are welcome!

⭐ Show Your Support

If you find this repository helpful, please consider giving it a star! It helps others discover these solutions.

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Note: This repository is maintained for educational purposes and interview preparation. All solutions are original implementations based on LeetCode problem descriptions.