Problem 11. Back and Forth Rows

What is wrong with this code please help me!

function c=back_and_forth(n)
y=n.^2;%expand the number x to x.^2 value because there must be x by x matrix
g=1:y;%expand the value 1 to y
f=reshape(g,n,n);%reshape g into x by x matrix
c=f';
end

Check this out.
function b = back_and_forth(n)
b=1:n^2;
b=reshape(b,n,n)';
for i=2:2:n
b(i,:)=fliplr(b(i,:));
end
end

my code works on my PC but not on this..

a = [1:(n^2)];
a = reshape(a,[],n)'

How can u do it in 10

I also want to know.

I can't write shorter program.

(^.^;)

very easy

gj

Why is this not working please?

a = ones(n,n);
for i = 1:n^2;
a(i) = i;
end
a = a'

I've tried this in school and it worked fine... :O Could you please help and explain? :)

Look closer at the requirements. Even rows should be flipped, such that their values are in descending order when reading from left-to-right.

Why is this problem showing errors in line 6 when I have a code of 4 line?

It works on matlab

i got same solution on matlab, but i don't know why i didn't here

good Question

really clever :)

Hi,
Could you comment how using str2num and anonymous functions decreases the score from 46 to 13? Is it a glinch in the notation system?
Regards

Hi, Florent.

The scoring in Cody is based on the number of nodes in the parse tree, and strings only require one node.

You can have a look for yourself by typing:
'>> mtree('back_and_forth.m','-file').show'.

Try to do it for the same code, without str2num, and you'll see that even small things like parenthesis or plus signs require their own node in the tree.

In terms of performance, the two versions are not so different. The problem here is that every solution, that use str2num in this way, will have the same Cody score, regardless of how elegant or efficient the anonymous function is.

I really like how you've split the matrix into two. That's a clever insight! And I am really interested in knowing WHY str2num requires only one node.

brilliant!

clever!
abs(sort(-cumprod(-ones(n)).*reshape(1:n^2,n,n)',2));
This one is more clear.what do you think?

well done,why can't come up with this method

Sorry, I just applied a slightly involved ans trick to the previous best solution. I hurts me though that the best solution involves a for loop.

This should work

This is faster and nicer than calling an external function to flip the direction.

Excellent