Merge Sort In Python
Chapter:
Python
Last Updated:
01-12-2020 13:20:57 UTC
Program:
/* ............... START ............... */
def merge_sort(arr):
if len(arr) <= 1:
return
mid = len(arr)//2
left = arr[:mid]
right = arr[mid:]
merge_sort(left)
merge_sort(right)
merge_two_sorted_lists(left, right, arr)
def merge_two_sorted_lists(a,b,arr):
len_a = len(a)
len_b = len(b)
i = j = k = 0
while i < len_a and j < len_b:
if a[i] <= b[j]:
arr[k] = a[i]
i+=1
else:
arr[k] = b[j]
j+=1
k+=1
while i < len_a:
arr[k] = a[i]
i+=1
k+=1
while j < len_b:
arr[k] = b[j]
j+=1
k+=1
if __name__ == '__main__':
test_cases = [
[10, 3, 15, 7, 8, 23, 98, 29],
[],
[3],
[9,8,7,2],
[1,2,3,4,5]
]
for arr in test_cases:
merge_sort(arr)
print(arr)
/* ............... END ............... */
Output
[3, 7, 8, 10, 15, 23, 29, 98]
[]
[3]
[2, 7, 8, 9]
[1, 2, 3, 4, 5]
Notes:
-
As like quick sort mergesort is uses divide and conquer rule. In merge sort we will divide the array and sort to make to one array.
- Please find the below steps in merge sort.
- Find the middle point of array by dividing into half.
- Call merge_sort (first half) to sort first half.
- Call merge_sort (first half) to sort Second half.
- merge_two_sorted_lists (firthalf,secondhalf,arr) function will sort the first half and second half to make to one aray.