# Copyright (c) 2015 Egor Tensin <Egor.Tensin@gmail.com>
# This file is part of the "Sorting algorithms" project.
# For details, see https://github.com/egor-tensin/sorting-algorithms.
# Distributed under the MIT License.
import sys
from ..algorithm import SortingAlgorithm
# Disclaimer: implemented in the most literate way.
def heapsort(xs):
_heapify(xs)
first, last = 0, len(xs) - 1
for end in range(last, first, -1):
xs[end], xs[first] = xs[first], xs[end]
_siftdown(xs, first, end - 1)
return xs
# In a heap stored in a zero-based array,
# left_child = node * 2 + 1
# right_child = node * 2 + 2
# parent = (node - 1) // 2
def _get_parent(node):
return (node - 1) // 2
def _get_left_child(node):
return node * 2 + 1
def _get_right_child(node):
return node * 2 + 2
def _heapify(xs):
last = len(xs) - 1
first_parent, last_parent = 0, _get_parent(last)
for parent in range(last_parent, first_parent - 1, -1):
_siftdown(xs, parent, last)
def _siftdown(xs, start, end):
root = start
while True:
# We swap if there is at least one child
child = _get_left_child(root)
if child > end:
break
# If there are two children, select the minimum
right_child = _get_right_child(root)
if right_child <= end and xs[child] < xs[right_child]:
child = right_child
if xs[root] < xs[child]:
xs[root], xs[child] = xs[child], xs[root]
root = child
else:
break
_ALGORITHMS = [
SortingAlgorithm('heapsort', 'Heapsort', heapsort),
]
def _parse_args(args=None):
if args is None:
args = sys.argv[1:]
return list(map(int, args))
def main(args=None):
xs = _parse_args(args)
print(heapsort(list(xs)))
if __name__ == '__main__':
main()
