recursion clear solution for Count Inversions by Cjkjvfnby - python coding challenges

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recursion solution in Clear category for Count Inversions by Cjkjvfnby

def count_inversion(sequence):
    head, *tail = sequence
    if tail:
        return sum(head > item for item in tail) + count_inversion(tail)
    else:
        return 0

Sept. 29, 2014

Comments:

tolemy on Feb. 15, 2015, 1:19 p.m.
nice and interesting! line2 is so cool, and it makes this recursion possible!

arma on March 8, 2015, 4:06 p.m.
Very original recursion solution. This technique is described here: <a href="https://www.python.org/dev/peps/pep-3132/">Extended Iterable Unpacking</a> It's unique Python3 feature: <a href="https://docs.python.org/3/whatsnew/3.0.html">https://docs.python.org/3/whatsnew/3.0.html</a>#new-syntax

Cjkjvfnby on March 10, 2015, 1:57 p.m.
unpacking and recursion is not related python3 has syntax sugar for a, b = lst[0], lst[1:]

arma on March 10, 2015, 8:25 p.m.
Sure. I've provided explanation link about Extended Iterable Unpacking technique on line 2, which is pretty unique thing. It might be useful for those who is not familiar with this syntax.

aussio on March 8, 2015, 7:21 p.m.
I really like this recursive approach. I figured there is probably a recursive solution to this. Very nice! :)

gnucian on June 21, 2015, 2:38 a.m.
Wow! Pretty nifty. I didn't know that I can call the function within its own definition.

CalebA.Kelley on July 26, 2015, 2:17 p.m.
I learned a lot today from the confusion this caused me. Thanks man!

M157q on Nov. 5, 2015, 1:20 p.m.
wow. I like this recursion version solution.

chzzz on Nov. 12, 2015, 7:21 a.m.
good solution

SungJunyoung on Nov. 12, 2015, 2:20 p.m.
Nice solution and I want to ask something! How I learn code like this (head, *tail = sequence...) I'm first in python and programming beginner I really want how you could write this beautiful code

laetrid on April 5, 2016, 2:13 p.m.
Hey, great!

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