Python/sorts/strand_sort.py
2022-11-15 14:55:14 +01:00

52 lines
1.3 KiB
Python

import operator
def strand_sort(arr: list, reverse: bool = False, solution: list | None = None) -> list:
"""
Strand sort implementation
source: https://en.wikipedia.org/wiki/Strand_sort
:param arr: Unordered input list
:param reverse: Descent ordering flag
:param solution: Ordered items container
Examples:
>>> strand_sort([4, 2, 5, 3, 0, 1])
[0, 1, 2, 3, 4, 5]
>>> strand_sort([4, 2, 5, 3, 0, 1], reverse=True)
[5, 4, 3, 2, 1, 0]
"""
_operator = operator.lt if reverse else operator.gt
solution = solution or []
if not arr:
return solution
sublist = [arr.pop(0)]
for i, item in enumerate(arr):
if _operator(item, sublist[-1]):
sublist.append(item)
arr.pop(i)
# merging sublist into solution list
if not solution:
solution.extend(sublist)
else:
while sublist:
item = sublist.pop(0)
for i, xx in enumerate(solution):
if not _operator(item, xx):
solution.insert(i, item)
break
else:
solution.append(item)
strand_sort(arr, reverse, solution)
return solution
if __name__ == "__main__":
assert strand_sort([4, 3, 5, 1, 2]) == [1, 2, 3, 4, 5]
assert strand_sort([4, 3, 5, 1, 2], reverse=True) == [5, 4, 3, 2, 1]