code<FONT creative solution for Mono Captcha by veky - python coding challenges

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

code<FONT solution in Creative category for Mono Captcha by veky

checkio=lambda I,S=lambda J,r=range:[{(i,j)for i in r(5)for j in r(3)if J[i][s+j
]%3}for s in r(1,len(J[0]),4)]:int("".join(min("1234567890",key=lambda i:len(g^S
((b"--X--XXX-XXX-X-X-XXX--XX-XXX-XXX--XX-XX--",
  b"-XX----X---X-X-X-X---X-----X-X-X-X-X-X-X-",
  b"--X---XX--X--XXX-XX--XXX--X--XXX-XXX-X-X-",
  b"--X--X-----X---X---X-X-X-X---X-X---X-X-X-",
  b"--X--XXX-XXX---X-XX---XX-X---XXX-XX---XX-"))[int(i)-1]))for g in S(I)))

Jan. 21, 2014

Comments:

veky on Jan. 21, 2014, 5:30 p.m.
As the title says, I managed to write code that's shorter than FONT (by line and character count). A few questions to think about if you're going to analyze the above code (in order of decreasing astonishment:): <ol> <li>What are those two lambdas doing after checkio=? How come one of them doesn't have a colon?</li> <li>What's that curious %3 doing between ] and } at the beginning of line 2?</li> <li>What is g^S at the end of line 2?</li> <li>Why is FONT in double parentheses? And what are those b's? Could I have saved a few chars there? (See, I'm not perfect.:)</li> <li>How did I manage to keep 0 at the end of FONT, instead of putting it at the beginning, where it would be much more logically placed (no, ordering in first argument of min actually has nothing to do with it)?</li> <li>Isn't [{( after first colon just so cute? :-D</li> </ol>

htamas on Jan. 23, 2014, 12:21 a.m.
In case you wanted actual answers: <blockquote> 1. What are those two lambdas doing after checkio=? How come one of them doesn't have a colon? </blockquote> The first one is the checkio() function, the second one is a helper function that will be called as S() from within checkio(). Both lambdas have a respective colon, but the second one comes a bit later in the code. <blockquote> 2. What's that curious %3 doing between ] and } at the beginning of line 2? </blockquote> It transforms ord('-') and ord('X') into 0 and 1 respectively, while preserving 0 and 1 themselves. <blockquote> 3. What is g^S at the end of line 2? </blockquote> Takes the symmetric difference between the sets of pixels in a digit from the analyzed image and a digit from the font. <blockquote> 4. Why is FONT in double parentheses? And what are those b's? Could I have saved a few chars there? (See, I'm not perfect.:) </blockquote> The first parenthesis is a function call, the second one is a tuple delimiter. The b's are there to avoid mapping the characters through ord(), since a bytes object already behaves like an array of integers. <blockquote> 5. How did I manage to keep 0 at the end of FONT, instead of putting it at the beginning, where it would be much more logically placed (no, ordering in first argument of min actually has nothing to do with it)? </blockquote> In the anonymous function used as the key for min, int(i)-1 evaluates to -1 for i=="0" and the -1th element of an array is the last one. <blockquote> 6. Isn't [{( after first colon just so cute? :-D </blockquote> No, it isn't. Ok, just kidding :). Finally, for the sake of those who would like to actually understand the code, here comes a slightly deobfuscated version: <pre class='brush: python'>FONT = (b"--X--XXX-XXX-X-X-XXX--XX-XXX-XXX--XX-XX--", b"-XX----X---X-X-X-X---X-----X-X-X-X-X-X-X-", b"--X---XX--X--XXX-XX--XXX--X--XXX-XXX-X-X-", b"--X--X-----X---X---X-X-X-X---X-X---X-X-X-", b"--X--XXX-XXX---X-XX---XX-X---XXX-XX---XX-") def makesets(image): digits = [] for s in range(1, len(image[0]), 4): pixels = {} for i in range(5): for j in range(3): if image[i][s+j] % 3: pixels.add((i,j)) digits.append(pixels) return digits def checkio(image): result = "" for g in makesets(image): def difference(i): return len(g ^ makesets(FONT)[int(i)-1]) result += min("1234567890", key=difference) return int(result) </pre>

veky on Jan. 23, 2014, 7:54 a.m.
Bravo, bravo, bravo. You got almost everything. (Yeah, I wanted actual answers, just maybe not so fast.:)) <blockquote> Could I have saved a few chars there? </blockquote> I could have saved 1 char, if I declared S to take *J instead of J (and then called it with *I at the end. That would cost me 1 char, (first * would be instead of space) but I'd have avoided double bracketing of FONT, saving 2. BTW, you haven't actually run the above code, right? :-) (I consider you very brave for that.:) In line 10, {} is a dict(), not a set() (unfortunate consequence of history of Python, where set came after dict and {} literal semantic was kept for backward compatibility). <blockquote> <h1>6. Isn't [{( after first colon just so cute? :-D</h1> </blockquote> (I was reflecting on how easy it is to build a list of sets of tuples with just nesting parentheses of the right type.)

veky on Jan. 23, 2014, 8:27 a.m.
Oh yeah, you missed to say that in <pre class='brush: python'>checkio=lambda I,S=lambda ... </pre> = in checkio=lambda and = in S=lambda are quite different: First is an assignment statement, second is specifying a default value for a named argument of checkio (which checkio will be called without, of course - so it'll use the default value, binding S to that lambda during execution of checkio). Of course, you surely know that already, but it might be puzzling for other people who tried to analyze the code, so since you already spoiled everything:-), this should be explained too.

oduvan on Jan. 23, 2014, 8:30 a.m.
Veky did you this back challenge to you ? :)

veky on Jan. 23, 2014, 8:33 a.m.
I your grammar quite don't understand. :-P (NHF, I know English is not native tongue, but I honestly can't see what you meant above.)

oduvan on Jan. 23, 2014, 8:43 a.m.
sorry I forgot a link <a href="http://www.checkio.org/forum/post/1485/vekyization-challenge/">http://www.checkio.org/forum/post/1485/vekyization-challenge/</a>

oduvan on Jan. 23, 2014, 8:44 a.m.
And I've just read again .. Sorry It doesn't make any sense.

htamas on Jan. 23, 2014, 3:10 p.m.
<blockquote> BTW, you haven't actually run the above code, right? :-) </blockquote> Of course :).

nickie on Feb. 15, 2014, 8:29 p.m.
Well done, although I'm not quite sure I understand how this is shorter than FONT. Do you mean, with the indentation in the answer template?

veky on Feb. 15, 2014, 11:50 p.m.
No, I mean the (rest of the) code, as opposed to FONT, which is just data. :-)

Dropbox

0 %

PyCharm The Python IDE for Professional Developers. Enjoy productive Python, web and scientific development with PyCharm. Download it now!