Solution for "All Permutations" speedy solution for All Permutations by zeixes - python coding challenges

Enable Javascript in your browser and then refresh this page, for a much enhanced experience.

Solution for "All Permutations" solution in Speedy category for All Permutations by zeixes

from collections.abc import Iterable
from itertools import permutations


def string_permutations(s: str) -> Iterable[str]:
    return sorted([''.join(chars) for chars in permutations(s)]) if s else []


print("Example:")
print(list(string_permutations("ab")))

# These "asserts" are used for self-checking
assert list(string_permutations("ab")) == ["ab", "ba"]
assert list(string_permutations("abc")) == ["abc", "acb", "bac", "bca", "cab", "cba"]
assert list(string_permutations("a")) == ["a"]
assert list(string_permutations("abcd")) == [
    "abcd",
    "abdc",
    "acbd",
    "acdb",
    "adbc",
    "adcb",
    "bacd",
    "badc",
    "bcad",
    "bcda",
    "bdac",
    "bdca",
    "cabd",
    "cadb",
    "cbad",
    "cbda",
    "cdab",
    "cdba",
    "dabc",
    "dacb",
    "dbac",
    "dbca",
    "dcab",
    "dcba",
]

print("The mission is done! Click 'Check Solution' to earn rewards!")

Nov. 30, 2023

Comments:

Nocturne13 on Jan. 19, 2024, 9:10 a.m.
, good one-liner

zeixes on Jan. 22, 2024, 10:15 a.m.
Thanks for your opinion. <a href="https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail"><a href="https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail</a>">https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail</a></a> Никаких вирусов.www.avast.com <a href="https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail"><a href="https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail</a>">https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail</a></a> <#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>

max_pro on April 3, 2024, 5:40 p.m.
No need to convert to list (the function sorted() does it already), and else statement is unnecessary, no need to output empty list. If input string(s) is empty then the output will be a list with empty string [''].

adamspj on May 5, 2024, 10:22 p.m.
The list comprehension is necessary for joining all the lists of char into strings unless we use map() which also creates a list before the sort. The if...else... may not be strictly necessary, but at least it saves a couple of function calls in case the function is called with an empty list. Average speed impact? I'm not sure.

zeixes on May 6, 2024, 9:04 a.m.
He about this sorted([''.join(chars) for chars in permutations(s)]) -> sorted(''.join(chars) for chars in permutations(s)) and he is right. Not neccessarry to create one more iterable object from existed.

adamspj on May 6, 2024, 6:11 p.m.
I see what you're getting at now, but notably, the version with the square brackets ran faster than the one without, now that I've tested it. Five repeats of 10000 executions, the list-comp version had a best time of 0.0127 sec and an average of 0.0135. The generator expression version had a best time of 0.0156 and average 0.0161. I'm new to learning about this stuff, so I'm not trying to pose as someone who knows more than I do. This is interesting and surprising to me. A Stack Overflow post addresses some version of this topic, and it seems the question of whether to prefer a list-comprehension vs. a generator expression depends on context. Before now, I hadn't taken the time to investigate this. <a href="https://stackoverflow.com/questions/9060653/list-comprehension-without-in-python">https://stackoverflow.com/questions/9060653/list-comprehension-without-in-python</a> P.S. I imagine that sort() and sorted() need access to a complete list in order to start sorting, i.e., sorting from a generator expression won't save time because sorted() can't know which item will come first in the sort until it's inspected all items, etc.

Strings and Integers

0 %

You ClassRoom Demo is Ready With the new tool CheckiO ClassRoom, you will be able to analyze your students' progress, have your own leaderboard, change missions order on the map, and so on.