LeetCode 75 Practice in Python

A structured project for practicing and mastering the LeetCode 75 essential coding interview questions in Python.

📋 Project Overview

This repository contains solutions to the LeetCode 75 curated list of essential interview questions, organized by problem type. Each solution includes:

• Clean, well-documented Python code
• Comprehensive test cases
• Time and space complexity analysis (where applicable)

🗂️ Project Structure

pytho-leetcode-75/
├── src/                          # Solution modules
│   ├── array_string/             # Array and String problems
│   ├── two_pointers/             # Two Pointers technique
│   ├── sliding_window/           # Sliding Window problems
│   ├── prefix_sum/               # Prefix Sum problems
│   ├── hash_map/                 # Hash Map/Set problems
│   ├── stack/                    # Stack problems
│   ├── queue/                    # Queue problems
│   ├── linked_list/              # Linked List problems
│   ├── binary_tree/              # Binary Tree - DFS problems
│   ├── binary_tree_bfs/          # Binary Tree - BFS problems
│   ├── binary_search_tree/       # Binary Search Tree problems
│   ├── graph_dfs/                # Graph - DFS problems
│   ├── graph_bfs/                # Graph - BFS problems
│   ├── heap/                     # Heap/Priority Queue problems
│   ├── binary_search/            # Binary Search problems
│   ├── backtracking/             # Backtracking problems
│   ├── dp_1d/                    # Dynamic Programming - 1D
│   ├── dp_multidimensional/      # Dynamic Programming - Multidimensional
│   ├── bit_manipulation/         # Bit Manipulation problems
│   ├── trie/                     # Trie problems
│   ├── intervals/                # Intervals problems
│   └── monotonic_stack/          # Monotonic Stack problems
├── tests/                        # Test files
├── requirements.txt              # Python dependencies
├── pyproject.toml                # Project configuration
├── pytest.ini                    # Pytest configuration
└── README.md                     # This file

🚀 Getting Started

Prerequisites

• Python 3.8 or higher
• pip (Python package installer)

Installation

1. Clone the repository:

git clone https://github.com/cd155/pytho-leetcode-75.git
cd pytho-leetcode-75

2. Install dependencies:

pip install -r requirements.txt

Or install with development dependencies:

pip install -e ".[dev]"

🧪 Running Tests

Run all tests:

pytest

Run tests for a specific problem:

pytest tests/test_merge_strings_alternately.py

Run tests with verbose output:

pytest -v

Run tests with coverage:

pytest --cov=src tests/

📝 Adding New Solutions

1. Create a solution file:

Create a new Python file in the appropriate category directory under src/. For example:

# src/array_string/your_problem.py
"""
LeetCode XXXX: Problem Title

Problem description here...
"""

class Solution:
    def yourMethod(self, input_param):
        """
        Solution description.
        
        Args:
            input_param: Description
            
        Returns:
            Description of return value
        """
        # Your implementation here
        pass

2. Create corresponding test file:

Create a test file in the tests/ directory:

# tests/test_your_problem.py
"""
Tests for LeetCode XXXX: Problem Title
"""

import pytest
import sys
from pathlib import Path

# Add src directory to path
src_path = Path(__file__).parent.parent / "src"
sys.path.insert(0, str(src_path))

from category.your_problem import Solution


class TestYourProblem:
    """Test cases for your problem"""
    
    def setup_method(self):
        """Setup test fixtures"""
        self.solution = Solution()
    
    def test_case_1(self):
        """Test description"""
        assert self.solution.yourMethod(input) == expected_output
    
    def test_case_2(self):
        """Test description"""
        assert self.solution.yourMethod(input) == expected_output

3. Run your tests:

pytest tests/test_your_problem.py -v

📊 Problem Categories

The LeetCode 75 problems are organized into the following categories:

1. Array / String - Basic array and string manipulation
2. Two Pointers - Problems using two pointer technique
3. Sliding Window - Window-based array/string problems
4. Prefix Sum - Cumulative sum techniques
5. Hash Map / Set - Hash table based problems
6. Stack - Stack data structure problems
7. Queue - Queue data structure problems
8. Linked List - Linked list manipulation
9. Binary Tree - DFS - Tree traversal with DFS
10. Binary Tree - BFS - Tree traversal with BFS
11. Binary Search Tree - BST specific problems
12. Graphs - DFS - Graph traversal with DFS
13. Graphs - BFS - Graph traversal with BFS
14. Heap / Priority Queue - Heap-based problems
15. Binary Search - Binary search algorithm
16. Backtracking - Backtracking technique
17. DP - 1D - One-dimensional dynamic programming
18. DP - Multidimensional - Multi-dimensional DP
19. Bit Manipulation - Bitwise operations
20. Trie - Trie data structure
21. Intervals - Interval-based problems
22. Monotonic Stack - Monotonic stack technique

🎯 Example Solution

See src/array_string/merge_strings_alternately.py for an example solution with:

• Detailed problem description
• Clean implementation
• Type hints
• Comprehensive docstrings

And tests/test_merge_strings_alternately.py for example test cases.

🤝 Contributing

Feel free to add more solutions or improve existing ones! Make sure to:

1. Follow the existing code structure
2. Add comprehensive test cases
3. Include docstrings and comments
4. Run tests before committing

📚 Resources

• LeetCode 75 Study Plan
• Python Documentation
• Pytest Documentation

📄 License

This project is for educational purposes. All LeetCode problems are property of LeetCode.

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Happy Coding! 🚀