Re: Container to map a vector of structures

From:
"Victor Bazarov" <v.Abazarov@comAcast.net>
Newsgroups:
comp.lang.c++
Date:
Thu, 26 Apr 2007 15:49:43 -0400
Message-ID:
<f0qvoo$mjm$1@news.datemas.de>
jeff_j_dunlap@yahoo.com wrote:

I recently began using STL containers, mainly to store pointers to
structures using a vector:
std::vector <dataStruc*> vdata;

Next, I fill the container within a loop:
vdata.push_back(new dataStruc(*it, param1, param2, param3);

Finally, traverse the vector within a loop (starting at the first
element and ending at the last) to create a report, thus, no random
access is required.

Now I have a new requirement and I need random access to each
structure contained in the vector. There will be thousands of
structures contained by my vector and I will be accessing structures
randomly multiple times--for instance, I may need to access any given
structure 10 or 20 times as I generate data for my report.

The easiest way I concieve this is to build a parallel vector that
stores the key string, such as:
std::vector <string> vKey;

Then I can 'seek' the string, obtain it's position, and using that
position, efficiently obtain the structure stored in the structure.

Would it be better to accomplish this with a different container, such
as a map or something else?


Probably. And if you have several such mappings, you can have several
maps, each setting the association between a key and the index of the
item in, say, a vector.

V
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