Re: Operation of STL vector
On 2007-05-11 17:53, Tony wrote:
Hello,
For my application, I have a vector containing data that I need,
vector<NODE> node_data; and I have a pointer of vectors which are
sorted by some criterion as vector<NODE*> np. I have planned the data
management as:
Whenever I want to add a new node, I push_back onto the end of
node_data and create a corresponding reference in np. However, I find
that only the last-added pointer in np correctly points to the right
location in memory of the NODE elements. My suspicion is that when
vector increases its size in memory, it completely reallocates a
larger space in memory such that the old references are no longer
valid. Is this true? i.e. when increasing the size of a vector, a
completely new structure is created in memory rather than just
"tacking on" an additional element at the end?
Not every time you add a new element but yes it happens.
If I wanted to be able to leave the old information alone, and
actually just "tack on" something at the end, would the List be a
better choice?
A list would work. However if you know from the beginning the number of
NODEs that will be pushed onto the vector you can use the reserve()
method to make sure that the vector can contain all the NODEs, in which
case it will not reallocate (as long as you don't add more NODEs than
your reserved.
Finally, could I get some suggestions for a "casual" book on
algorithms (as far as casual they can be!) for a hobbyist programmer?
Do you want an algorithm book, describing different types of algorithms
and analyses them, or a book describing how to implement different
algorithms and data structures in a specific language, or do you want a
book about how to effectively use the data structures and algorithms
that comes with standard C++?
You'll probably get the most benefit (at least in the short term) with
the last kind of book and a highly recommended one is The C++ Standard
Library: A Tutorial and Reference by Nicolai M. Josuttis. I don't know
of any good books of the second kind (not saying that there are none,
just that I don't know of any) and the first kind can be a bit much for
a hobbyist.
--
Erik Wikstr?m