how to understand to write merge sort algorithm python code example
Example 1: Merge Sort python
def merge_sort(arr):
if len(arr) <= 1:
return arr
mid = len(arr) // 2
left, right = merge_sort(arr[:mid]), merge_sort(arr[mid:])
return merge(left, right, arr.copy())
def merge(left, right, merged):
left_cursor, right_cursor = 0, 0
while left_cursor < len(left) and right_cursor < len(right):
if left[left_cursor] <= right[right_cursor]:
merged[left_cursor+right_cursor]=left[left_cursor]
left_cursor += 1
else:
merged[left_cursor + right_cursor] = right[right_cursor]
right_cursor += 1
for left_cursor in range(left_cursor, len(left)):
merged[left_cursor + right_cursor] = left[left_cursor]
for right_cursor in range(right_cursor, len(right)):
merged[left_cursor + right_cursor] = right[right_cursor]
return merged
Example 2: merge sort in python
def mergeSort(myList):
if len(myList) > 1:
mid = len(myList) // 2
left = myList[:mid]
right = myList[mid:]
mergeSort(left)
mergeSort(right)
i = 0
j = 0
k = 0
while i < len(left) and j < len(right):
if left[i] < right[j]:
myList[k] = left[i]
i += 1
else:
myList[k] = right[j]
j += 1
k += 1
while i < len(left):
myList[k] = left[i]
i += 1
k += 1
while j < len(right):
myList[k]=right[j]
j += 1
k += 1
myList = [54,26,93,17,77,31,44,55,20]
mergeSort(myList)
print(myList)