Try out this test problem first.
Given the variable x as your input, multiply it by two and put the result in y.
Examples:
Input x = 2 Output y is 4
Input x = 17 Output y is 34
Press the "Solve This Now!" button below to get started...
Solution Stats
Problem Comments
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52 Comments
Show
49 older comments
Sam Nazari
on 9 Apr 2012
Why does y = bitshift(x,1); give a larger solution size than the most common answer listed so far?
Manuel Ignacio
on 6 Feb 2013
The first problem. Very easy but enough to start the Cody Game. Great game!
Adrian Dronca
on 7 Mar 2013
@Sam Nazari
I guess it`s because calling bitshift makes the code size bigger. You call a function.
When there is only x*2 its 1 operation only.
JeremyR
on 20 Jun 2013
Deceivingly easy start to the game!
raviraja
on 11 Dec 2013
Ha ha I got it
Ruchi Agarwal
on 13 Feb 2014
Great!
Matthew Brown
on 16 Dec 2014
I did in fact start here.
Alan Martinez
on 23 Dec 2014
Good problem for beginners.
Prita Vaidya
on 30 Nov 2015
Nice!!!
Pedro Pascual González
on 30 Nov 2015
Yeah
Brendan Hofmann
on 8 Dec 2015
cool
Acylos
on 5 Jan 2016
alright
Roberto
on 5 Mar 2016
I tried to use bitshift but I forgot it doesn't work with x<0
Daniel E. Loza Morales
on 12 May 2016
Easy starter problem. Except I was expecting Cody, to require a '.m' file upload.
Mashharar Bhuiyan
on 28 Aug 2016
very basic,very interesting indeed
pixi
on 27 Oct 2016
test
Reenu Thomas
on 13 Dec 2016
Very interesting!
Muhammad M Sahari
on 17 Dec 2016
good for newcomers
Ashley Jacob
on 17 Dec 2016
interesting
sim yoke meng
on 20 Dec 2016
interesting!
nour eddin
on 24 Dec 2016
good questionsss
Adi Zabidi
on 27 Dec 2016
1st try :)
Abubaker SHERIF
on 29 Dec 2016
like
Dixon Chen
on 29 Dec 2016
ez
Nazmi Azim Azmi
on 29 Dec 2016
GG
MAX LIM ZHENG CONG
on 30 Dec 2016
nice
Mohan Shanmugam
on 9 Jan 2017
nice
SIVAPRAKASH DANABALASINGAM
on 10 Jan 2017
good job
Devan Rao
on 10 Jan 2017
good job
Chris Shaw
on 26 Jan 2017
nice
N/A
on 30 Apr 2017
good
Multiplexer
on 4 Aug 2017
ok
Adrian Quesada
on 22 Aug 2017
This is the best way to start using Cody
TK
on 16 Oct 2017
This is the best problem to start using Cody.
Jason Webster
on 16 Oct 2017
Instructions say to press the "Solve This Now!" button, but there is no such button...
Mohamed Atyya
on 30 Oct 2017
good
Rodney Foster
on 6 Dec 2017
grade
Meg Noah
on 27 Dec 2017
I submitted the following, which works in my version of matlab, but it found errors and said it wasn't valid:
function y = times2(x)
% Modify the line below so that the output y is twice the incoming value x
y = bitsll(x,fi(1));
% After you fix the code, press the "Submit" button, and you're on your way.
end
Tan Shuwen is pig
on 11 Jan 2018
The beginning of the dream!
Veera Kanmani
on 21 Mar 2018
this is nice..
TY Wang
on 24 Mar 2018
Smooth
TY Wang
on 24 Mar 2018
What is the meaning of these axises
Laczi Dániel
on 23 May 2018
nice...
Dyuman Joshi
on 8 Jun 2018
No one can solve this.
Hardest problem ever.
Abdelfatah Teamah
on 25 Sep 2018
nice problem
qiang zhang
on 10 Oct 2018
a new starting
Vivek Singh
on 16 Jan 2019
Nice problem
Daniel Cooper
on 8 Mar 2019
Nice
testsiddhi siddhi
on 19 Jul 2019
Sherlock Bugcrowd
on 4 Oct 2019
Nice problem for beginners
Xiao Zehn
on 5 Oct 2019
nice
Dan Xu
on 8 Nov 2019 at 16:12
Great for test, like Hello world.
Solution Comments
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1 Comment
dan
on 17 Nov 2019 at 7:48
novice lalala...
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1 Comment
Nhat Lam Nguyen
on 10 Sep 2019
nice
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1 Comment
DIMI EKONGA NZELLY
on 25 Jun 2019
easy
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1 Comment
xiaoyong
on 15 May 2019
Start
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2 Comments
Benedikt Gasparic
on 3 Nov 2018
Bugfest lmao can this program even read basic matlab? fix your shit
anas anas
on 13 Mar 2019
awesome <3
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3 Comments
albert huarhua tupayachi
on 15 Aug 2018
good!
Vivek Singh
on 15 Aug 2018
nice one
Fragrant Sun
on 24 Oct 2018
nice!!
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2 Comments
Antonios Meimaris
on 9 Jul 2018
Leading solution size is 0???
madhan ravi
on 10 Jul 2018
don't know how the leading solution is calculated;/
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1 Comment
Corentin OGER
on 21 Feb 2019
Ach! even bigger than mine, you cheater!
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1 Comment
nadhirahjasri
on 20 Sep 2017
this is fun!
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2 Comments
Adrian Quesada
on 22 Aug 2017
This is the best way to star using Cody
TY Wang
on 24 Mar 2018
!
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1 Comment
Matthias Witkowski
on 8 Aug 2017
one step at atime
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1 Comment
Markus Raith
on 9 Jul 2017
Nice starter
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1 Comment
Foufa.h
on 8 Apr 2017
very easy
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1 Comment
Henry Lu
on 28 Mar 2017
Go ahead
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1 Comment
Shuo Wang
on 10 Feb 2017
why the leading solution size is 0
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1 Comment
SIVAPRAKASH DANABALASINGAM
on 10 Jan 2017
very easy
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1 Comment
Devan Rao
on 10 Jan 2017
easy
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3 Comments
MAX LIM ZHENG CONG
on 30 Dec 2016
nice
MEI HUEI LIM
on 30 Dec 2016
nice
SIVAPRAKASH DANABALASINGAM
on 10 Jan 2017
nice
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2 Comments
Gerard Chen
on 30 Dec 2016
nice
SIVAPRAKASH DANABALASINGAM
on 10 Jan 2017
hi
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2 Comments
TAYALAN SIVALINGAM
on 29 Dec 2016
easy
SIVAPRAKASH DANABALASINGAM
on 10 Jan 2017
nice
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2 Comments
Nur Yashmeira Yassin
on 29 Dec 2016
:)
SIVAPRAKASH DANABALASINGAM
on 10 Jan 2017
good job
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2 Comments
Suheib Sherif
on 29 Dec 2016
This was my first!
SIVAPRAKASH DANABALASINGAM
on 10 Jan 2017
good job
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2 Comments
JAEHYUK WOO
on 13 Oct 2016
easy!!
SIVAPRAKASH DANABALASINGAM
on 10 Jan 2017
good job yar
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1 Comment
David Verrelli
on 3 Sep 2018
This user appears to have gamed the system, with fraudulent "likes" of this unremarkable solution submitted by 'sock-puppet' accounts. —DIV
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2 Comments
Ravi
on 29 Mar 2016
bitshift(-3,1)
ans =
-6
SIVAPRAKASH DANABALASINGAM
on 10 Jan 2017
good job yar
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2 Comments
Alo
on 12 Mar 2016
Nice
SIVAPRAKASH DANABALASINGAM
on 10 Jan 2017
good job yar
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3 Comments
Abdullah Momoh
on 9 Jan 2016
Addition is used instead of multiplication as it will take a shorter amount of time to compute
SIVAPRAKASH DANABALASINGAM
on 10 Jan 2017
good job yar
Corentin OGER
on 21 Feb 2019
Haha, well done!
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2 Comments
Matthew Atilano
on 6 Dec 2015
It might help to put in the variable x.
SIVAPRAKASH DANABALASINGAM
on 10 Jan 2017
good job yar
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2 Comments
Daniel Jenkinson
on 4 Dec 2015
Is there a way to make y autoupdate when you change the value of x?
SIVAPRAKASH DANABALASINGAM
on 10 Jan 2017
good job yar
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2 Comments
Sierra McGee
on 9 Nov 2015
This is a basic solution, everyone should be able to solve this.
SIVAPRAKASH DANABALASINGAM
on 10 Jan 2017
good job yar
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3 Comments
Ruth tannert
on 30 Sep 2015
i did it!!!
Jakub Mrowka
on 19 Sep 2016
gz
SIVAPRAKASH DANABALASINGAM
on 10 Jan 2017
good job yar
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2 Comments
Matt Brennan
on 7 Sep 2015
Step 1 complete
SIVAPRAKASH DANABALASINGAM
on 10 Jan 2017
good job yar
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2 Comments
korraprolu brahma
on 3 Jun 2015
trying the best
SIVAPRAKASH DANABALASINGAM
on 10 Jan 2017
good job yar
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1 Comment
Alexander Wickstrom
on 28 May 2015
Is it necessary to use the . after 2?
Couldn't you write y = 2*x; ?
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1 Comment
Sebastian Cuenca
on 26 Apr 2015
Yeah, i do it
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1 Comment
Matthew Caron
on 7 Jan 2015
This was a great starter question.
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1 Comment
asdasdasd
on 26 Dec 2014
what is the correct answer??
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1 Comment
Khieu
on 4 Mar 2014
What this solution is wrong?
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1 Comment
Divya
on 16 Jan 2014
Is it wrong?
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1 Comment
Emilio
on 18 Nov 2013
how do you improve this solution?
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2 Comments
Anand Abhishek Singh
on 24 Sep 2013
how leading solution size is 0?
Clayton
on 11 Nov 2013
Probably hacked something
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1 Comment
Greg
on 9 Sep 2013
So really, the name of the game is to pass only the assertion tests; as opposed to the description of the problem.
Definitely not seeing how to get a solution size 0...
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19 Comments
Show
16 older comments
Greg
on 9 Sep 2013
What the heck is freepass?
Ramesh Vukyam
on 23 Oct 2013
Is this a solution ?
J.R.! Menzinger
on 10 Feb 2014
Nice place to test... ;-)
Alison
on 20 May 2014
cute but ridiculous
213
on 28 Jun 2014
why it's 'freepass.please',not other words else?
Alfonso Nieto-Castanon
on 28 Jun 2014
'freepass' is just a (cute but ridiculous) hack (see problem http://www.mathworks.com/matlabcentral/cody/problems/1774-free-passes-for-everyone ). The 'please' part is because we are really polite...
Pinakin
on 20 Apr 2015
hello Alfonso !
I'd like to know how the solution size for your solution to the 'times two' question is '0'
can you please explain ?
thanks !
Erenca
on 29 Oct 2015
how is this even possible, solution with 0 size?
Dan Po
on 24 Sep 2016
does freepass; still work?
Mostafa
on 26 Oct 2016
"Leading Solution is 0".. Just.. How?!
Aditya Jain
on 26 Oct 2016
I rescored this solution and it failed
Alfonso Nieto-Castanon
on 26 Oct 2016
@Aditya: I do not appreciate this solution being rescored, this particular solution had historical value to me, but obviously not to you
Aditya Jain
on 26 Oct 2016
The reason I rescored your solution is because a solution cannot have a size of 0. With respect to your comment on the historical value, I think the solution is still there and I haven't changed that. If you still believe its an error from my side, you can email ned.gulley@mathworks.com and we can discuss it further.
Aditya Jain
on 26 Oct 2016
Another solution is that you could use your free pass trick and rescore this solution again. I just don't want the solution to have a size of 0.
Alfonso Nieto-Castanon
on 26 Oct 2016
Zero-score solutions have some history in Cody (see problem 42396). This solution was the only zero-score freepass solution (all other passing freepass solutions got a score of 100 for good reasons), so having this solution now fail the test removes its score and hence its significance. In any way, this is all fine and just a game, I just think it would be sad to see all of the other solutions in Cody that got zero, negative, maxint or other "impossible" scores being rescored for no good reason (#endofgetoffmylawnrant)
Aditya Jain
on 26 Oct 2016
Good Point. I speak to Ned about this and discuss whether we should keep such solutions or not.
Thanks for the input and sorry for the trouble. #peace
Aditya Jain
on 26 Oct 2016
@Alfonso: I have reverted back my change :)
Alfonso Nieto-Castanon
on 27 Oct 2016
that's fantastic, thanks!
Corentin OGER
on 21 Feb 2019
Tried the freepass command on my computer, all I get is
Undefined variable "freepass" or class "freepass.please".
Also I have no idea how code size is calculated
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2 Comments
ABHAY SONI
on 7 Dec 2012
can anyone tell me why this is incorrect
Ned Gulley
on 12 Mar 2013
I see two problems. It needs to be a function (as modeled by the template), and the input command hangs and times out when called by a web service.
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6 Comments
Show
3 older comments
Dirk Engel
on 27 Jun 2012
It works, but it's ugly :-)
Chang Ho
on 6 Aug 2012
Nice! :)
Marlies
on 16 Nov 2012
Never realized that MATLAB sees a defined assignment (y = 2*x) different than no assignment (2*x => assignment to ans).
If anything, I would have guessed the second would be (slightly) more effort.
Zaka
on 23 Mar 2013
does this variable "ans" overrides MATLAB's default "ans"?
David Amor
on 27 Apr 2013
ok, i got there in the end. but it defeats the rules - there is no "y" variable when you change the template to ans = times2(x)...
how do you know what the rules are?!?
Ankith Rathod
on 15 Jul 2018
comment section gives a great info
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1 Comment
Justyna Zander
on 3 Apr 2012
Missing test cases:
assert(isequal(times2(0),0));
assert(isequal(times2(0.1),0.2));
assert(isequal(times2(0.000001),0.000002));
assert(isequal(times2(0.1000000000001),0.2000000000002));
assert(isequal(times2(1.0000000000000000000000000000001),2));
assert(isequal(times2(-0),0));
... and a few others.
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3 Comments
Jan
on 26 Jan 2012
The test suite is weak. Please add:
assert(isequal(times2(Inf), Inf))
assert(isequal(times2(NaN), NaN))
assert(isequal(times2([]), []))
assert(isequal(times2(magic(3)), 2*magic(3)))
Jan
on 26 Jan 2012
To focus the power of Matlab, add these tests:
assert(isequal(times2(Inf), Inf)) assert(isequal(times2(NaN), NaN))
assert(isequal(times2([]), [])) assert(isequal(times2(magic(3)), 2*magic(3)))
Spring Dawn
on 25 Sep 2018
nice
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