Python MergeSort

MergeSort

def merge(numbers, i, j, k):
    merged_size = k - i + 1               # Size of merged partition
    merged_numbers = [0] * merged_size    # Dynamically allocates temporary array
                                          # for merged numbers
    merge_pos = 0                         # Position to insert merged number
    left_pos = i                          # Initialize left partition position
    right_pos = j + 1                     # Initialize right partition position
   
    # Add smallest element from left or right partition to merged numbers
    while left_pos <= j and right_pos <= k:
        if numbers[left_pos] <= numbers[right_pos]:
            merged_numbers[merge_pos] = numbers[left_pos]
            left_pos += 1
        else:
            merged_numbers[merge_pos] = numbers[right_pos]
            right_pos += 1
        merge_pos = merge_pos + 1
   
    # If left partition is not empty, add remaining elements to merged numbers
    while left_pos <= j:
        merged_numbers[merge_pos] = numbers[left_pos]
        left_pos += 1
        merge_pos += 1
   
    # If right partition is not empty, add remaining elements to merged numbers
    while right_pos <= k:
        merged_numbers[merge_pos] = numbers[right_pos]
        right_pos = right_pos + 1
        merge_pos = merge_pos + 1
   
    # Copy merge number back to numbers
    for merge_pos in range(merged_size):
        numbers[i + merge_pos] = merged_numbers[merge_pos]


def merge_sort(numbers, i, k):
    j = 0

    if i < k:
        j = (i + k) // 2  # Find the midpoint in the partition

        # Recursively sort left and right partitions
        merge_sort(numbers, i, j)
        merge_sort(numbers, j + 1, k)
            
        # Merge left and right partition in sorted order
        merge(numbers, i, j, k)