__ clear solution for Rotate Hole by Cjkjvfnby - python coding challenges

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__ solution in Clear category for Rotate Hole by Cjkjvfnby

def rotate(state, pipe_numbers):
    size = len(state)
    return [i for i in range(size) if all(state[(x - i) % size] for x in pipe_numbers)]

July 9, 2014

Comments:

ArchTauruS on Sept. 29, 2014, 2:41 a.m.
smart one!

ruska87 on May 28, 2015, 2:41 p.m.
Tell please, why "% size" ?

dunpealer on Aug. 14, 2015, 1:39 p.m.
It seems that you are right, the `'% size'` is not needed because of Python's negative index behavior.

han97 on Aug. 30, 2016, 3:41 p.m.
Python's negative index behaviour doesn't make the same. For example. l = [1,2,3,4,5]. And l[15 % len(l)] isn't the same as l[15] (The last one throws IndexError). and l[-15] isn't the same as l[-15%len(l)]

Eldin on Jan. 22, 2016, 1:23 p.m.
You're so close, why not make it a on-liner :D

aya.kanazawa on May 4, 2019, 5:24 a.m.
x is pipenumber which we want to check, i is rotatenumber ``` x=0 i=0 size=12 ((x - i) % size)=0 x=1 i=0 size=12 ((x - i) % size)=1 x=0 i=1 size=12 ((x - i) % size)=11 x=1 i=1 size=12 ((x - i) % size)=0 x=0 i=2 size=12 ((x - i) % size)=10 x=1 i=2 size=12 ((x - i) % size)=11 x=0 i=3 size=12 ((x - i) % size)=9 ``` This solution works, but I can't recognize why ``` -1 % 12 = 11 ```

aya.kanazawa on May 4, 2019, 5:44 a.m.
I solved the above by myself. ``` 12 * div + mod = -1 12 * -1 + mod = -1 # div must be - mod = -1 + 12 = 11 ```

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