📚 Significantly enhance repository documentation and code comments

[Copilot]

This PR transforms the LeetCode Solutions repository from a basic code collection into a comprehensive, well-documented learning resource. The changes address the need for better documentation throughout the repository.

🎯 Problem Addressed

The repository previously had minimal documentation:

• Basic 18-line README with limited information
• No problem categorization or navigation aids
• Missing code explanations and complexity analysis
• No clear repository structure documentation
• Lack of contributing guidelines and usage examples

📈 Major Improvements

Enhanced Main README.md

• Comprehensive Overview: Added detailed description with repository statistics (50+ solutions across Java/C++)
• Organized Problem Index: Created categorized tables with direct LeetCode links, organized by difficulty (Easy/Medium/Hard)
• Clear Navigation: Added usage examples, file organization explanation, and quick reference guides
• Professional Formatting: Enhanced with emojis, tables, and structured sections for better readability
• Improved Contributing Guidelines: Added code quality standards, naming conventions, and submission process

Individual Solution Documentation

Enhanced three complex solutions with comprehensive documentation:

1043. Partition Array for Maximum Sum (Dynamic Programming)

/**
 * Problem: Given an integer array arr, partition it into sub-arrays of at most k elements.
 * Approach: Dynamic Programming with rolling array optimization
 * Time Complexity: O(n * k)
 * Space Complexity: O(k)
 */

76. Minimum Window Substring (Sliding Window)

/**
 * Problem: Return the minimum window substring containing all characters from target string
 * Approach: Sliding Window with Two Pointers and frequency mapping
 * Time Complexity: O(|s| + |t|)
 * Space Complexity: O(1)
 */

1463. Cherry Pickup II (3D Dynamic Programming)

/**
 * Problem: Two robots collect cherries moving down a grid
 * Approach: 3D DP with memoization, handling 9 movement combinations
 * Time Complexity: O(m * n^2)
 * Space Complexity: O(m * n^2)
 */

🔍 Key Features Added

Repository Statistics Dashboard

• 50+ total solutions with language breakdown
• Problem range: #2 to #3330
• Difficulty distribution: ~30% Easy, ~50% Medium, ~20% Hard
• Topics covered: Arrays, Strings, Trees, DP, Graphs, etc.

Navigation Improvements

• Direct links to all LeetCode problems
• Categorized problem tables by difficulty
• Usage examples for running solutions
• Quick reference sections for easy discovery

Code Quality Enhancements

• Detailed algorithm explanations and approach documentation
• Time/space complexity analysis for complex solutions
• Comprehensive inline comments explaining logic
• Edge case documentation and optimization notes

📊 Impact

This documentation enhancement transforms the repository from a simple code collection into a structured learning resource that:

• Improves discoverability with organized problem indices
• Enhances learning with detailed explanations and complexity analysis
• Facilitates contribution with clear guidelines and standards
• Provides better navigation with direct links and categorization

The repository now serves as both a reference for solutions and an educational resource for understanding algorithmic approaches.

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