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Merged
merged 4 commits into from
Sep 29, 2020
Merged

Update sorts/quick_sort_3_partition.py #2507

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a30a283
Update sorts/quick_sort_3partition.py
taseikyo Sep 29, 2020
85f2e81
Update sorts/quick_sort_3_partition.py
taseikyo Sep 29, 2020
1a983e3
Update sorts/quick_sort_3_partition.py
taseikyo Sep 29, 2020
38f2fc3
Update sorts/quick_sort_3_partition.py
taseikyo Sep 29, 2020
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21 changes: 12 additions & 9 deletions sorts/quick_sort_3_partition.py
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Original file line number Diff line number Diff line change
@@ -1,4 +1,4 @@
def quick_sort_3partition(sorting: list, left: int, right: int) -> list:
def quick_sort_3partition(sorting: list, left: int, right: int):
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Why this change?

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quick_sort_3partition does not return a new list, it just updates in place. So I remove -> list.

if right <= left:
return
a = i = left
Expand All @@ -18,25 +18,28 @@ def quick_sort_3partition(sorting: list, left: int, right: int) -> list:
quick_sort_3partition(sorting, b + 1, right)


def quick_sort_3part(sorting: list) -> list:
def three_way_radix_quicksort(sorting: list) -> list:
"""
Another quick sort algorithm, returns a new sorted list
Three-way radix quicksort:
https://en.wikipedia.org/wiki/Quicksort#Three-way_radix_quicksort
First divide the list into three parts.
Then recursively sort the "less than" and "greater than" partitions.

>>> quick_sort_3part([])
>>> three_way_radix_quicksort([])
[]
>>> quick_sort_3part([1])
>>> three_way_radix_quicksort([1])
[1]
>>> quick_sort_3part([-5, -2, 1, -2, 0, 1])
>>> three_way_radix_quicksort([-5, -2, 1, -2, 0, 1])
[-5, -2, -2, 0, 1, 1]
>>> quick_sort_3part([1, 2, 5, 1, 2, 0, 0, 5, 2, -1])
>>> three_way_radix_quicksort([1, 2, 5, 1, 2, 0, 0, 5, 2, -1])
[-1, 0, 0, 1, 1, 2, 2, 2, 5, 5]
"""
if len(sorting) <= 1:
return sorting
return (
quick_sort_3part([i for i in sorting if i < sorting[0]])
three_way_radix_quicksort([i for i in sorting if i < sorting[0]])
+ [i for i in sorting if i == sorting[0]]
+ quick_sort_3part([i for i in sorting if i > sorting[0]])
+ three_way_radix_quicksort([i for i in sorting if i > sorting[0]])
)


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