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From: Jack on 1 May 2010 04:44
Dear all,

std::vector<x> finalvector;
std::vector<x> x1;
std::vector<std::vector<x>> x2;


for (...)
{
for (...) {
x1.push_back(data);
}
x2.push_back(x1);
}

std::vector<std::vector<x>>::reverse_iterator it;
for (it = x2.rbegin(); it != x2.end(); it++)
{
finalvector.push_back(**it); <<<<<<<<<<<<< compilation error
}

I'd like to reverse a grid in a y-axis while keeping the x-axis components
intact.

For example
1 2 3 4 5 6 7 8
a b c d e f g h

to

a b c d e f g h
1 2 3 4 5 6 7 8

Is it the correct way of doing it?
Thanks in advance
Jack



From: Jack on 1 May 2010 04:58
> for (it = x2.rbegin(); it != x2.end(); it++)

Sorry, typo x2.rend(), still doesn't compile
Thanks


From: David Lowndes on 1 May 2010 08:40
>std::vector<x> finalvector;

finalvector should be the same type as x2, i.e.:

std::vector<std::vector<x>> finalvector;

and then use:

finalvector.push_back( *it );

However, an easier solution is to use:

#include <algorithm>

std::reverse( x2.begin(), x2.end() );

Dave
From: Jack on 1 May 2010 08:49
Thanks David,
I'll give it a try!
Jack


From: Stephan T. Lavavej [MSFT] on 1 May 2010 23:33
You should point out that std::reverse() will be significantly more
efficient. It swaps instead of copying.

In general, it's a good idea to use Standard Library algorithms whenever
possible. Their designers and implementers worked hard to make them as
efficient as possible. Using Standard Library containers is simply the first
step.

Stephan T. Lavavej
Visual C++ Libraries Developer

"David Lowndes" <DavidL(a)example.invalid> wrote in message
news:l68ot5dlo896r90nrmj0jejgnoiku68ek7(a)4ax.com...
> >std::vector<x> finalvector;
>
> finalvector should be the same type as x2, i.e.:
>
> std::vector<std::vector<x>> finalvector;
>
> and then use:
>
> finalvector.push_back( *it );
>
> However, an easier solution is to use:
>
> #include <algorithm>
>
> std::reverse( x2.begin(), x2.end() );
>
> Dave

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