Problem 19. Swap the first and last columns

size is 10 ??????
how to finish it?

Not too shabby

GOOD

GOOD

Clever solution!

good problem

Nice problem.

Is The Test Suite 3 right?

B=A
B(:,end) = A(:,1);
B(:,1) = A(:,end);

nice

x = A(:,1);
y = A(:,end);
A(:,1)=y;
A(:,end)=x;
B=A

function B = swap_ends(A)
B=A;
[r,c]=size(A);
B(:,1)=A(:,c);
B(:,c)=A(:,1);
end

Why isn´t my code working? And why isn´t B_correct = [32051] (test 3) the right answer?

niceee

not a general solution, will fail A=[1;2]. Use size iso lengt

function B = swap_ends(A)
B = A(:,[end , 2:end-1 , 1]);
end

why its not working ??

@Zunaed It doesn't work because it fails the 4th test case of A = [1]. I used that same code in the MATLAB software and it outputs B = [1 1] instead of B = [1] since you're printing out the last and first element of the matrix. You only should be printing [1] not [1 1]

Se vuoi ti faccio un paio di ripetizioni swap a 5$

If Anybody can help me i strongly grateful to him

Could fail the last test, if A has only 1 column:
c = 1
Bad indexing (r,c-1) == (r,0)

You got to catch case c = 1 and don't swap at all

And................ obviosly
"Undefined function or variable 'C1'."
You have made assignments in wrong order.
Your code says: A(:,1)=C1
Should say: C1 = A(:,1);

B = A;
B(:,[1 end]) = A(:,[end 1]);

Really an impressing answer!

A good one

there is problem on this exam

fliplr flips all elements in rows. The problem say only 'flip' the first one and the last one

That should work

B = A([end, 2:end-1, 1])

Why isn't this acceptable?

B = A(:,[end, 2:end-1, 1])

When A is a number,end-1=0;it will be wrong;

function [B] = swap_ends(A)
%SWAP_ENDS Solution 19: Swap the first and last columns
if length(A)>1
B=cat(2,A(:,length(A)),A(:,2:length(A)-1),A(:,1));
else
B=A;
end

end

nice

length not correct, use size(A,2)

.

B=permute(A,4:1) ?

A couple of comments:
(1) The first case of setting B=1 when there is only one column in A will satisfy the test case on Cody, for which A=[1], but is not a general solution. For example, it would not generate the correct output if A=[7], nor if A=[1; 1].
(2) You have six separate, but identical, evaluations of size(A,2)). It would seem to make sense to evaluate this once only, and to assign it to a variable.
(3) Although your structure of three separate "if" statements clearly works, you could consider using instead "elseif" and "else" within a single "if" statement. Alternatively you could also use "switch, case, otherwise".

test 3 for correctness is wrong

test 3 is error

please correct the test suite.
Test 3 B_correct is wrong:
where you test B_correct=[3 5 0 2 1]
it should be B_correct=[3 2 0 5 1]

No, this solution does not cover size(A,2)==2.

the ultimate solution to all problems

cheater.

Hmm isn't it a shortest instruction ? :/ any tips ? :)

esta mal evaluado este ejercicio

Normally, after writing an A matrix, as I write like A(:,1)=A(:,end); , it is giving the actual result. Where is the mistake ?

You need to change both ends.

test suite #3 is wrong, i think

It works perfectly on Matlab. No idea why this says it failed...

For A=1, it returns B=[1 1] because A(:,end) and A(:,1) are both 1. It should return B=1. Hope this helps.

Thanks James! I figured it out

In the problem description a valid solution should also work for a 1-column matrix with more than one 1 row, like [4; 2]: "If the input has one column, the output should be identical to the input."

But solution 170924 submitted on 30 Nov 2012 (Size: 23, the leading solution) does not work in this case.

I wonder why such a case is not evaluated by the test suite.

Most probably not considered by the author while submitting the problem.

However, a test case with single column array has been added and solutions have been rescored.

In this function you need only to OVERWRITE the first and last columns, not regenerate the whole thing. for example: A(:,[1 end]) = A(:,[end 1]);

the third case also works !!!

My MATLAB worked for Test#3:
>> swap_ends(A)

ans =

3 2 0 5 1

Strange??

This solution works just fine on my matlab..why is cody returning: "Undefined function 'cody.verifyCode' for input arguments of type 'char'."

i dont understand why this code is not working

function B = swap_ends(A)
C = A(:,1);
D = A(:,2:end-1);
E = A(:,end);
B = [E D C];
end

Granted I'm replying to an old post, but the problem with the solution given is when A is just a single number. A = 1;

Need to improve test 3. center cols are symmetric, so even though cols 2 and 4 get swapped, the test suite can't validate.

like the fliplr, this solution is invalid... the test suite is limited.

invalid solution, it also affects the middle columns
It passes because the test suite only tests for symmetrical matrices :/

Wrong code! Not just the first and last columns swapped!

Incorrect solution. If the array has only one column, this solution generates two columns.

Actually this solution works just fine. Try it in MATLAB. It doesn't create two columns.

You can't just do B = A(:,[end,1])...this would end up two columns if A has only one column. You should do A(:,[1,end]) = A(:,[end,1])) and then B = A

The test suite does not properly test solutions to this problem. This solution would fail for
A = [ 12 4 5 7
5 1 2 4];

Incorrect solution

Invalid solution. If the array has one column, this solution generates two columns.