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Optimization for shell sort #4038

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Merged
merged 3 commits into from
Dec 18, 2020
Merged

Optimization for shell sort #4038

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6c32a6d
fixed shell sort
realDuYuanChao Dec 16, 2020
b020f35
udpate code style
realDuYuanChao Dec 17, 2020
cf44cf3
Update sorts/shell_sort.py
realDuYuanChao Dec 18, 2020
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19 changes: 6 additions & 13 deletions sorts/shell_sort.py
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Original file line number Diff line number Diff line change
@@ -1,13 +1,5 @@
"""
This is a pure Python implementation of the shell sort algorithm

For doctests run following command:
python -m doctest -v shell_sort.py
or
python3 -m doctest -v shell_sort.py

For manual testing run:
python shell_sort.py
https://en.wikipedia.org/wiki/Shellsort#Pseudocode
Comment on lines 1 to +2
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I would leave the first line like this

Suggested change
"""
This is a pure Python implementation of the shell sort algorithm
For doctests run following command:
python -m doctest -v shell_sort.py
or
python3 -m doctest -v shell_sort.py
For manual testing run:
python shell_sort.py
https://en.wikipedia.org/wiki/Shellsort#Pseudocode
"""
This is a Python implementation of the shell sort algorithm.
Reference: https://en.wikipedia.org/wiki/Shellsort#Pseudocode

"""


Expand All @@ -25,15 +17,16 @@ def shell_sort(collection):
[-45, -5, -2]
"""
# Marcin Ciura's gap sequence

gaps = [701, 301, 132, 57, 23, 10, 4, 1]
for gap in gaps:
for i in range(gap, len(collection)):
insert_value = collection[i]
j = i - gap
while j >= 0 and insert_value < collection[j]:
collection[j + gap] = collection[j]
j = i
while j >= gap and insert_value < collection[j - gap]:
collection[j] = collection[j - gap]
j -= gap
collection[j + gap] = insert_value
collection[j] = insert_value
return collection


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