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lonewolff

Erasing an element in a vector

6 posts in this topic

Hi Guys,

I am pretty new to std::vectors and have a quick question.

If I iterate through the vector like so...

[code]std::vector<ClientSocketData>::iterator it;
for(it=Client.begin();it<Client.end();it++)
{
// delete current item from list if certain condition is met
}[/code]
...how can I delete / remove the item that is currently in use?

Your help is greatly appreciated. :cool:
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[code]for (it = client.begin(); it != client.end(); ) {
if (condition == true)
it = client.erase(it);
else
++it;
}[/code]
[quote name='lonewolff' timestamp='1306410237' post='4815999']
Hi Guys,

I am pretty new to std::vectors and have a quick question.

If I iterate through the vector like so...

[code]std::vector<ClientSocketData>::iterator it;
for(it=Client.begin();it<Client.end();it++)
{
// delete current item from list if certain condition is met
}[/code]
...how can I delete / remove the item that is currently in use?

Your help is greatly appreciated. :cool:
[/quote]
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i think you'd better take a look at erase-remove idiom about vector.it's a efficient way to remove element in vector
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[quote name='Yang G' timestamp='1306467591' post='4816284']
i think you'd better take a look at erase-remove idiom about vector.it's a efficient way to remove element in vector
[/quote]

erase-remove of a std::vector uses the swap and pop method, correct?
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No, but it will only copy an object to be retained at most once, whereas the algorithm triangles presented can move an object many times. It also maintains the original relative ordering, probably not important for client sockets but a desirable trait sometimes (e.g. swap-and-pop on a render list of sprites can result in some sprites suddenly drawing themselves on top of other sprites they had previously been "behind").

I believe the algorithm is something like this:
[code]
def remove_if(begin, end, predicate)
{
write = begin
for(read = begin ; read != end ; ++read)
{
if(!predicate(*read))
{
if(read != write)
{
*write = *read
}
++write
}
}
return write
}
[/code]
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[quote name='lpcstr' timestamp='1306488604' post='4816356']
[quote name='Yang G' timestamp='1306467591' post='4816284']
i think you'd better take a look at erase-remove idiom about vector.it's a efficient way to remove element in vector
[/quote]

erase-remove of a std::vector uses the swap and pop method, correct?
[/quote]
it's like that
[code]
template < class ForwardIterator, class T >
ForwardIterator remove ( ForwardIterator first, ForwardIterator last, const T& value )
{
ForwardIterator result = first;
for ( ; first != last; ++first)
if (!(*first == value))
*result++ = *first;
return result;
}
[/code]
(from c++ library).
Note:
remove doesn't delete the element in the vector instead of overwriting the element like the code said.
so we must use erase to delete these elements who should be removed like that vec.erase(remove(first, end, value), end).
you can see these subjects in book named Effective STL
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