How to Sort Using Merge Sort Method in Python?

Here is how to sort using Merge Sort method in Python.
Run the code here: https://repl.it/@VinitKhandelwal/merge-sort

#mergeSort function to break lists into halves

def mergeSort(list1):

  # if list size is just 1 then no sorting required

  length = len(list1)

  if length < 2:

    return list1

  # cutting lists into middle

  middle = int(length/2)

  left = list1[0:middle]

  right = list1[middle:]

  #first mergeSort until splitted completely, then merge

  return merge(mergeSort(left),mergeSort(right))

# merge function to merge back all splitted lists

def merge(left, right):

  result = []

  leftIndex = 0

  rightIndex = 0

  # compare and merge

  while leftIndex < len(left) and rightIndex < len(right):

    if left[leftIndex] < right[rightIndex]:

      result.append(left[leftIndex])

      leftIndex += 1

    else:

      result.append(right[rightIndex])

      rightIndex += 1

  #merge remaining

  return result + left[leftIndex:] + right[rightIndex:]

print(mergeSort([6,4,2,8,7,1,3,0,9,5]))

OUTPUT

[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

BIG O

O(n log n)

Comments

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