LeetCode Exercise Repository

Welcome to my LeetCode solutions repository! 🎯

This repository contains a collection of LeetCode problems I have solved, written in C++ and accompanied by detailed explanations for every solution. The main goal of this repository is to serve as a learning reference for anyone who wants to understand how to solve LeetCode problems — not just the working code, but also the reasoning behind every algorithm and data structure choice.

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📑 Table of Contents

• Purpose of This Repository
• Repository Structure
• Writing Conventions & Style
• Problem Index
• How to Learn from / Contribute to This Repo
• Roadmap & Targets
• Prerequisites
• License

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🎯 Purpose of This Repository

1. Personal Documentation — An archive of LeetCode solutions I have completed, with a strong focus on quality and clarity.
2. Learning Reference — A reference point for others who want to:
   • Understand problem reformulation (transforming a problem into a mathematical/algorithmic form).
   • See trade-offs between algorithms (e.g., BFS vs. Dijkstra vs. 0-1 BFS).
   • Study time and space complexity along with their justifications.
   • Follow a line-by-line code walkthrough with concrete examples.
3. High Code Standards — Every solution is documented with:
   • Algorithm choice based on the problem's constraints.
   • Big-O complexity analysis.
   • Memory layout and overhead.
   • A verification checklist to validate correctness.

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📂 Repository Structure

explore-project/
├── README.md
└── leetcode-exercise/
    ├── <problem-slug>/
    │   ├── solution.cpp              # C++ solution source
    │   └── solution-explanation.md   # Detailed explanation + walkthrough
    └── ...

Folder Naming

Each problem folder uses its LeetCode slug (lowercase, separated by -). Example: find-the-safest-path-in-a-grid/

Contents of Each Problem Folder

File	Description
solution.cpp	Solution implementation in C++ (typically only the Solution class, matching the LeetCode standard).
solution-explanation.md	Comprehensive write-up: problem reformulation, algorithm, complexity, line-by-line walkthrough, example-based verification.

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✍️ Writing Conventions & Style

Every solution-explanation.md follows a consistent 11-section structure:

1. Problem Reformulation — Re-stating the problem in a form that is easier to solve algorithmically.
2. Algorithm Choice — Discussion of why a particular algorithm is selected, including the alternatives considered.
3. Step-by-Step Walkthrough — Detailed explanation of each step with tables and pseudocode.
4. Variable Definitions — Table describing the meaning of every variable.
5. Verification with Examples — Validation using LeetCode sample inputs.
6. Complexity Analysis — Big-O time & space complexity, with justification.
7. DSA Choices — Why Each — Comparison table explaining why each data structure is used.
8. Memory Layout — Estimated byte footprint for every component.
9. Correctness Argument — A brief proof of algorithmic correctness.
10. Verification Checklist — List of properties that have been verified.
11. Line-by-Line Code Walkthrough — A detailed code explanation with simulation on a small input.

Coding Principles

• C++17 as the minimum standard.
• STL only — no external dependencies.
• Minimum time & space complexity — always pick the most efficient solution that remains easy to understand.
• Consistent variable naming — nr, nc for neighbor, r, c for current, s/ns for score, dq for deque, pq for priority queue, etc.
• English content for solutions and explanations (the universal technical standard).

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📚 Problem Index

#	Problem	LeetCode #	Topics	Algorithm	Folder
1	Find the Safest Path in a Grid	2812	Grid BFS, Max-Heap, Widest Path	Multi-source BFS + Dijkstra (max-heap)	find-the-safest-path-in-a-grid
2	Find a Safe Walk Through a Grid	3286	Grid, Shortest Path, 0-1 Weights	0-1 BFS with deque	find-a-safe-walk-through-a-grid

📌 This table will be updated as new problems are added.

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🚀 How to Learn from / Contribute to This Repo

For Readers (Learning Path)

1. Open the folder of the problem you want to study.
2. Read solution-explanation.md before opening solution.cpp to build intuition.
3. Once you understand the algorithm, open solution.cpp and match it with the explanation.
4. Try re-implementing the solution without looking at the code as practice.
5. Run the solution on LeetCode to verify correctness.

For Contributors (Adding a New Problem)

If you would like to add a new problem, follow the existing structure:

leetcode-exercise/<problem-slug>/
├── solution.cpp
└── solution-explanation.md

Make sure the explanation covers at minimum:

• Problem reformulation
• Algorithm + justification
• Time & space complexity
• Verification with examples
• Line-by-line walkthrough

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🗺️ Roadmap & Targets

• Add new problems on a regular basis
• Categorize problems by difficulty tier (Easy / Medium / Hard)
• Add topic categories (Array, Graph, DP, Greedy, etc.)
• Auto-generate a problem index by topic
• Multi-language versions (C++ + Python) for selected problems

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🛠️ Prerequisites

• A C++ compiler with C++17 support (e.g., g++ ≥ 7, clang++ ≥ 5, or MSVC 2017+).
• Standard headers used: <vector>, <deque>, <queue>, <array>, <algorithm>, <climits>, etc.

Example compilation:

g++ -std=c++17 -O2 -Wall -o solution solution.cpp

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📄 License

This repository is released under the MIT License — free to use for learning, reference, or contribution, provided that attribution is preserved.

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💬 Contact & Feedback

If you have feedback, corrections, or suggestions for improving any of the solution explanations, please feel free to open an Issue or Pull Request in this repository.

"The best way to learn is to teach." — Happy coding! 🚀