Add Merge Sort implementation in C

[Abhi8756]

📋 Pull Request Description

What does this PR add?

• New algorithm implementation
• Data structure implementation
• New programming language support
• Language-specific README
• Bug fix
• Documentation improvement
• Test cases

Algorithm/Feature Details

• Name: Merge Sort
• Language: C
• Category: Sorting Algorithms
• Time Complexity: O(n log n) for all cases
• Space Complexity: O(n) for temporary arrays

Testing

• Code compiles without errors (syntax verified)
• All test cases covered in main function
• Edge cases handled (invalid input, empty arrays)
• Documentation updated with comprehensive comments

Algorithm Features

• Divide-and-conquer approach: Recursively divides array into halves
• Stable sorting: Maintains relative order of equal elements
• Consistent performance: O(n log n) for best, average, and worst cases
• Memory management: Proper malloc/free for temporary arrays
• Interactive input: User can enter custom array to sort
• Comprehensive output: Shows original vs sorted array plus algorithm info

Additional Notes

• Follows repository's C coding style (matches selection_sort.c format)
• Uses dynamic memory allocation for temporary arrays during merge process
• Includes proper error handling for invalid input
• Algorithm information displayed to educate users about complexity
• Clean, readable C code with detailed comments explaining the divide-and-conquer process
• Implements both merge() helper function and recursive mergeSort() function

Hacktoberfest 2025

This contribution is part of Hacktoberfest 2025 participation. Merge sort was missing from the C sorting algorithms collection and is a fundamental algorithm that demonstrates divide-and-conquer methodology.

[github-actions]

🎉 Welcome to Hacktoberfest 2025, @Abhi8756! 🎃

Thank you for your first contribution to our DSA repository! Here's what happens next:

🔍 Automatic Checks

• ✅ Code Validation: Passed
• 🧪 Compilation Tests: Passed

📋 Next Steps

🎯 Great job! Your code compiled successfully. Maintainers @Karanjot786 and @Pradeepsingh61 will review your PR soon.

🎁 What You Get

• 🏆 Hacktoberfest Credit: This PR counts toward your 6 PR goal for exclusive T-shirt + Tree!
• 🌟 Hall of Fame: You'll be featured in our contributors list
• 📚 Learning: Code review feedback from experienced developers

💡 Tips for Success

• Follow our Contributing Guidelines
• Add comments explaining your algorithm
• Include time/space complexity analysis
• Test your code before submitting

Welcome to the community! 🚀

[github-actions]

🤖 Automated PR Status

🔍 Code Validation

✅ Passed - File naming and structure look good!

🧪 Compilation Tests

✅ Passed - All code compiles successfully!

📋 Overall Status

🎉 Ready for Review - Your PR has passed all automated checks!
👥 Maintainers have been notified for review.

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This comment was generated automatically. Checks will re-run when you push new commits.

[Karanjot786]

it is good @Pradeepsingh61 now you can merge it

[github-actions]

🎉 Welcome to Hacktoberfest 2025, @Abhi8756! 🎃

Thank you for your first contribution to our DSA repository! Here's what happens next:

🔍 Automatic Checks

• ✅ Code Validation: Passed
• 🧪 Compilation Tests: Passed

📋 Next Steps

🎯 Great job! Your code compiled successfully. Maintainers @Karanjot786 and @Pradeepsingh61 will review your PR soon.

🎁 What You Get

• 🏆 Hacktoberfest Credit: This PR counts toward your 6 PR goal for exclusive T-shirt + Tree!
• 🌟 Hall of Fame: You'll be featured in our contributors list
• 📚 Learning: Code review feedback from experienced developers

💡 Tips for Success

• Follow our Contributing Guidelines
• Add comments explaining your algorithm
• Include time/space complexity analysis
• Test your code before submitting

Welcome to the community! 🚀

[github-actions]

🤖 Automated PR Status

🔍 Code Validation

✅ Passed - File naming and structure look good!

🧪 Compilation Tests

✅ Passed - All code compiles successfully!

📋 Overall Status

🎉 Ready for Review - Your PR has passed all automated checks!
👥 Maintainers have been notified for review.

---

This comment was generated automatically. Checks will re-run when you push new commits.