What is a merge sort in C and how is it implemented?

Table of Contents

• Introduction
• How Merge Sort Works
  • Key Steps:
• Implementation of Merge Sort in C
  • Step 1: Split the Array
  • Step 2: Merge the Sorted Arrays
  • Merge Sort Code in C
  • Code Explanation:
  • Output:
• Practical Example: Sorting an Array of Numbers
• Conclusion

Introduction

Merge Sort is a popular sorting algorithm that follows the divide-and-conquer approach. It recursively splits an array into two halves, sorts each half, and merges the sorted halves back together. Merge sort is efficient and stable, with a time complexity of O(n log n), making it suitable for large datasets.

In this guide, we will explore how merge sort works and provide a step-by-step implementation in the C programming language.

How Merge Sort Works

Key Steps:

1. Divide the array into two halves.
2. Recursively sort each half.
3. Merge the two sorted halves to create the final sorted array.

The merging process ensures that the resulting array is sorted by comparing elements from both halves and inserting them in the correct order.

Implementation of Merge Sort in C

Step 1: Split the Array

The array is split recursively until each sub-array has only one element, which is considered sorted.

Step 2: Merge the Sorted Arrays

The merge() function combines two sorted sub-arrays into one sorted array by comparing their elements.

Merge Sort Code in C

Code Explanation:

1. mergeSort():
   • Recursively divides the array into two halves.
   • Calls the merge() function to combine the sorted halves.
2. merge():
   • Merges two sorted sub-arrays into one sorted array by comparing elements from both halves.
3. printArray():
   • Prints the array elements to verify the sorting process.

Output:

Practical Example: Sorting an Array of Numbers

Let's modify the code to sort an array of exam scores using merge sort:

This implementation will output the scores in ascending order after sorting with merge sort.

Conclusion

Merge sort is an efficient and reliable sorting algorithm, especially for large datasets, due to its O(n log n) time complexity. Its recursive nature, combined with the merging of sorted arrays, ensures optimal sorting performance. Although it requires additional space for temporary arrays, merge sort remains a stable and preferred choice for sorting operations where memory usage isn't a critical concern. Understanding how merge sort works and its implementation in C allows you to handle sorting tasks efficiently in various applications.