Problem 1. Times 2 - START HERE

Created by Cody Team

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...

Problem Group

Cody Challenge

Solve This Now!

4716 solvers submitted 7419 solutions (1.57 solutions/solver).

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Problem Comments

10 players like this problem

4 Comments

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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.

Jeremy on 20 Jun 2013 at 20:43

Deceivingly easy start to the game!

Solution Comments

Solution 174526

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.

Solution 103340

5 players like this solution

5 Comments

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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?!?

Solution 70013

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.

Solution 7097

1 player likes this solution

2 Comments

Jan Simon 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)))