Hi,
I have a vector of strings. I want to hold it only unique strings.
That is, before adding any new string, I want to check if it is already
present, and if yes, then I will not add the new item.
Is there a simpler and efficient way of doing it (instead of traversing
linearly through the whole list and comparing strings everytime I want to
add new item).
Thanks in advance,
Abhishek
5  4037 
Abhishek Pandey wrote: Hi,
I have a vector of strings. I want to hold it only unique strings.
That is, before adding any new string, I want to check if it is already
present, and if yes, then I will not add the new item.
Is there a simpler and efficient way of doing it (instead of traversing
linearly through the whole list and comparing strings everytime I want to
add new item).
std::map should be an obvious alternative to vector.
Perhaps the best alternative would be a hash container, but that's not
part of the standard stl, although many stl implementations have one.
So, *must* it be a vector, or can you change the container ?
"Gianni Mariani" <gi*******@mari ani.ws> wrote in message
news:nN******** ************@sp eakeasy.net... Abhishek Pandey wrote: Hi,
I have a vector of strings. I want to hold it only unique strings.
That is, before adding any new string, I want to check if it is already
present, and if yes, then I will not add the new item.
Is there a simpler and efficient way of doing it (instead of traversing
linearly through the whole list and comparing strings everytime I want
to add new item).
std::map should be an obvious alternative to vector.
Perhaps the best alternative would be a hash container, but that's not
part of the standard stl, although many stl implementations have one.
So, *must* it be a vector, or can you change the container ?
Thanks for the reply,
Changing the container will require more code changes, which I was trying to
avoid if possible.
-Abhishek
Abhishek Pandey wrote:
"Gianni Mariani" <gi*******@mari ani.ws> wrote in message
news:nN******** ************@sp eakeasy.net... Abhishek Pandey wrote: Hi,
I have a vector of strings. I want to hold it only unique strings.
That is, before adding any new string, I want to check if it is already
present, and if yes, then I will not add the new item.
Is there a simpler and efficient way of doing it (instead of traversing
linearly through the whole list and comparing strings everytime I want to add new item).
std::map should be an obvious alternative to vector.
Perhaps the best alternative would be a hash container, but that's not
part of the standard stl, although many stl implementations have one.
So, *must* it be a vector, or can you change the container ?
Thanks for the reply,
Changing the container will require more code changes, which I was trying to
avoid if possible.
How do you build up the vector?
Is it built in one rush or are things added as needed?
If the former then a possible solution is:
Just add all of the strings (you will have duplicates now).
Then sort the vector. In this way all the duplicates will be
at consecutive vector positions. Walk through the vector and
remove the duplicates.
Look up: std::sort std::unique
--
Karl Heinz Buchegger kb******@gascad .at
"Karl Heinz Buchegger" <kb******@gasca d.at> wrote in message
news:41******** *******@gascad. at... Abhishek Pandey wrote:
"Gianni Mariani" <gi*******@mari ani.ws> wrote in message
news:nN******** ************@sp eakeasy.net... Abhishek Pandey wrote:
> Hi,
> I have a vector of strings. I want to hold it only unique strings.
> That is, before adding any new string, I want to check if it is
already > present, and if yes, then I will not add the new item.
> Is there a simpler and efficient way of doing it (instead of
traversing > linearly through the whole list and comparing strings everytime I
want to > add new item).
std::map should be an obvious alternative to vector.
Perhaps the best alternative would be a hash container, but that's not
part of the standard stl, although many stl implementations have one.
So, *must* it be a vector, or can you change the container ?
Thanks for the reply,
Changing the container will require more code changes, which I was
trying to avoid if possible.
How do you build up the vector?
Is it built in one rush or are things added as needed?
If the former then a possible solution is:
Just add all of the strings (you will have duplicates now).
Then sort the vector. In this way all the duplicates will be
at consecutive vector positions. Walk through the vector and
remove the duplicates.
I add the things as and when needed and not in one go. :-(
Thanks
Look up: std::sort std::unique
--
Karl Heinz Buchegger
kb******@gascad .at
make sure the vector is sorted at all times, then before you insert, do
a binary search.
or just use std::set.
If you cannot change the order of elements in the vector, then maintain
a separate std::set using the minimal data needed to define uniqueness.
-shez-
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