Re: map or set for handling struct with a key?

"Victor Bazarov" <>
Wed, 8 Aug 2007 15:53:00 -0400
Digital Puer wrote:

Hi, I was wondering whether to use a map or a set for
my purposes.

I am reading rows from a database and am populating a
struct (or class) for each row. It has a key and ancillary
data, e.g.:

struct Foo {
 int key;
 float data1;
 int data2;
 string data3;

Now I want to keep all the rows in either a map or a set.
If I use a set, I can keep the struct the way it is; the only
thing I need is to provide a comparison function for the set
so that the ordering is based on the key.

On the other hand, if I use a map, I am inclined to break
the key out and use the key as the first part in the map,

struct Foo {
 float data1;
 int data2;
 string data3;
map<int, Foo> mydata;

Which approach is preferable for the following cases:

1. My only operations on the data structure are to iterate
over it and to use find().

2. I will iterate over as well as update the data.

If you don't update the keys, ever, then you're better off with
a sorted vector/deque.

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