First clear solution for Count Inversions by gyahun_dash - python coding challenges

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First solution in Clear category for Count Inversions by gyahun_dash

import itertools as it

def count_inversion(sequence):
    return sum(x > y for x, y in it.combinations(sequence, 2))

Sept. 3, 2014

Comments:

pdtpatrick on Nov. 9, 2014, 4:14 p.m.
Nice. combinations didn't cross my mind. Very cool.

gyahun_dash on Nov. 13, 2014, 3:43 p.m.
Thank you. Itertools often helps me.

l2032 on Jan. 10, 2015, 1:39 p.m.
nice, good to know combinations exists. I really need to get more acquainted with the existing libraries.

saxtouri on Jan. 12, 2015, 10:45 p.m.
CHEATING! Nice, though.

baozhao123 on April 2, 2015, 12:53 a.m.
yes, my final solution like this one

PyPoet on Sept. 1, 2015, 6:50 p.m.
That's one of the niftiest ways of cheating I've seen so far... Do I assume correctly that this exploits the behavior of itertools.combinations() to start with the leftmost element and proceed in a linear fashion?

Nithin on Oct. 23, 2015, 9:23 a.m.
I'm sorry, why is this considered cheating?

PyPoet on Oct. 23, 2015, 7:40 p.m.
Actually, I don't think there is such a thing as cheating in programming. If my assumption from above is correct, you could call this solution a hack, since it (legitimately) exploits the behavior of a module in order to do something it was not designed/expected/intended to do. Thus, I rather expressed my astonishment than disapproval when I called it cheating. After all, gyahun_dash left all the heavy lifting to python/itertools instead of coding the challenging parts by himself... like less proficient coders would (i.e. noobs like me and inside-the-box-thinkers). Out of curiosity: How would you characterize this approach? Cheers!

tarjeii on Oct. 30, 2015, 4:56 p.m.
nice

M157q on Nov. 5, 2015, 1:05 p.m.
wow. don't know can use combinations here. GJ

Hayertjez on Nov. 18, 2015, 11:38 a.m.
For me it is not clear what this function does.

dana77 on Jan. 23, 2016, 8:28 p.m.
I also had to first either try it out or look it up. After I typed the following in the py shell everything was clear. <pre class='brush: python'>import itertools as it for i in it.combinations(sequence, 2): print(i) </pre>

Franky on Dec. 17, 2015, 7:35 a.m.
combinations is exactly what we need here!

TheFreshman on Jan. 30, 2016, 11:59 p.m.
Very cool! I didn't realize you could use itertools that way.

ljy95135 on May 24, 2016, 9:36 a.m.
Yes, it's fastest way to code.

2010min0ru on Oct. 22, 2020, 12:45 p.m.
Nice usage of a itertools.combinations!

Ulukai85 on Aug. 13, 2021, 6:34 a.m.
That is really clever! I often shy away from combinations because I fear the complexity, but that doesn't seem to be a problem here. Have to try it more often!

bravebug on Sept. 13, 2021, 6:25 a.m.
best!

uran33 on Nov. 11, 2021, 2:37 p.m.
I was looking for something similar for another task. Thank you.

Tomatenkopf on April 8, 2023, 12:10 p.m.
My god, never thought to use combinations here... so clever! Thank you!

Nocturne13 on May 1, 2023, 8:52 a.m.
Why I sometimes have troubles with combinations, because it demands lots of resources and takes much time to execute the script, but in this task it works brilliant. Well done!

Magu on Nov. 21, 2023, 12:52 p.m.
good use of itertools.combinations! combinations('ABCD', 2) ---> AB AC AD BC BD CD cool indeed.

H0r4c3 on Nov. 15, 2024, 6:24 p.m.
Great solution! Nice use of itertools.combinations() combinatoric generator.

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