I need to access each element in a vector and also know what index the element is in.
So far I could come up with two ways
for (iterator it= aVector.begin(), int index= 0; it!= aVector.end(); ++it, ++index)
leaving the type signature. also it looks like i can't use auto
for (int index = 0; index < aVector.size(); ++index)
{
// access using []
}
Which one is more efficient or is there a better way to do this?
The answer is in the question - "know what index the element is in.".
So -
for (int index = 0; index < aVector.size(); ++index)
{
// access using []
}
Performance-wise they're the same (but you can always profile yourself).
for (iterator it = aVector.begin(), int index= 0; it!= aVector.end(); ++it, ++index)
This will not compile. But it doesn't really matter, because as long as we are talking about std::vector then accessing by index is a simple pointer arithmetic and dereference - so in reality as fast as with the iterator. So your version 2 is OK.
I would however further optimize (if you are really concerned about speed):
for (int index = 0, size = aVector.size(); index < size; ++index)
{
// access using []
}