Code Notes made by Vaibhav Rathod

Merge Sort

2 min read

Written by Vaibhav Rathod

Explanation

  • Merge Sort is a divide-and-conquer sorting algorithm. It divides the list into smaller sublists, sorts each sublist recursively, and then merges the sorted sublists to produce the final sorted list.

Steps:

  • If the list has more than one element, split it into two halves.
  • Recursively apply the same operation on both halves.
  • Merge the two sorted halves into a single sorted list.
  • Repeat the process until the list is sorted.

Time Complexity:

  • Best Case, Average Case, Worst Case: O(n log n)
def merge_sort(arr):
    if len(arr) > 1:
        # Find the middle of the array
        mid = len(arr) // 2
        left_half = arr[:mid]
        right_half = arr[mid:]
 
        # Recursively sort both halves
        merge_sort(left_half)
        merge_sort(right_half)
 
        # Merge the sorted halves
        i = j = k = 0
        while i < len(left_half) and j < len(right_half):
            if left_half[i] < right_half[j]:
                arr[k] = left_half[i]
                i += 1
            else:
                arr[k] = right_half[j]
                j += 1
            k += 1
 
        # Check if any element was left in the left or right half
        while i < len(left_half):
            arr[k] = left_half[i]
            i += 1
            k += 1
        while j < len(right_half):
            arr[k] = right_half[j]
            j += 1
            k += 1
 
# Example usage
arr = [38, 27, 43, 3, 9, 82, 10]
merge_sort(arr)
print("Sorted array is:", arr)

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