red floyd wrote:
Quote:
Stefan Naewe wrote:
Quote:
>Ian Collins schrieb:
Quote:
>>Alan wrote:
>>> Is there an easy and efficient way to combine two <vector>s, rather
>>>than taking each element from one and adding it to the other?
>>>>
>>> I haven`t been able to find any guidance on or examples of this
>>>sort of operation.
>>>>
>>vector1.insert( vector1.end(), vector2.begin(), vector2.end() );
>>>
>>
>It's easy - yes.
>But is it really efficient ?
>Isn't it as unefficient as repeatedly calling push_bask() on vector1 ?
>
Why does everyone ask "is this more efficient" in a vacuum?
>
Have you benchmarked to determine that your vector operations are the
bottleneck? An "efficient" program that doesn't work right is not as
good as an "inefficient" program that does.
>
And how is changing from push_back to insert going to make this code not
work right?
Quote:
Hoare's Law (also attributed to Knuth): "Premature optimization is the
root of all evil".
Okay, let's all use bubble sort until we can prove that quicksort will
be a better choice.
Sometimes optimization without measurement is perfectly appropriate.
When there's a choice of two ways to do something and one is slower,
choose the other.
for (iter = vector2.begin(); iter != vector2.end(); ++iter)
vector1.push_back(*iter);
versus
vector1.insert(vector1.end(), vector2.begin(), vector2.end());
No contest. Use the latter.
--
-- Pete
Roundhouse Consulting, Ltd. (
www.versatilecoding.com)
Author of "The Standard C++ Library Extensions: a Tutorial and
Reference." (
www.petebecker.com/tr1book)
