Skip to content
Permalink
master
Switch branches/tags

Name already in use

A tag already exists with the provided branch name. Many Git commands accept both tag and branch names, so creating this branch may cause unexpected behavior. Are you sure you want to create this branch?
Go to file
 
 
Cannot retrieve contributors at this time
"""mergesort.py - implementation of mergesort. """
__author__ = "Caleb Madrigal"
__date__ = "2015-02-13"
def merge(left, right):
if len(left) < 1:
return right
elif len(right) < 1:
return left
else:
first_left, *rest_left = left
first_right, *rest_right = right
if first_left <= first_right:
return [first_left] + merge(rest_left, right)
else:
return [first_right] + merge(left, rest_right)
def mergesort(lst):
list_len = len(lst)
if list_len < 2:
return lst
if list_len == 2:
if lst[0] <= lst[1]:
return lst
else:
return [lst[1], lst[0]]
else: # list_len > 2
split_point = list_len // 2
left = lst[0:split_point]
right = lst[split_point:]
left_sorted = mergesort(left)
right_sorted = mergesort(right)
return merge(left_sorted, right_sorted)
if __name__ == "__main__":
import unittest
testsuite = unittest.TestLoader().discover('test', pattern="*mergesort*")
unittest.TextTestRunner(verbosity=1).run(testsuite)