Re: STL set lower_bound

From:

Paavo Helde <paavo@nospam.please.ee>

Newsgroups:

comp.lang.c++

Date:

Sun, 29 Mar 2009 16:39:46 -0500

Message-ID:

<Xns9BDE6BEA8EB1nobodyebiee@216.196.109.131>

mattg <gara.matt@gmail.com> kirjutas:

On Mar 29, 2:24?pm, Paavo Helde <pa...@nospam.please.ee> wrote:

mattg <gara.m...@gmail.com> kirjutas:
[...]

void test(){
? ? ?s1.insert((new node(1)));
? ? ?s1.insert((new node(2)));
? ? ?s1.insert(new node(8));
? ? ?s1.insert(new node(9));
? ? ?s1.insert(new node(12));

[...]

? ? ?iter = s1.lower_bound(new node(5));

outputs

iter = 8

instead of

iter = 2

?

Because that's how lower_bound is defined:

"Returns an iterator to the first element in a set with a key that is
equ

to or greater than a specified key"

If you want the previous element, you can check the result against
s1.beg

() and decrement the iterator.

hth
Paavo

so something like:

if(iter != s1.begin())
{
node* lessthan = *(--iter); //this is the node less than the query
}

Yes, something like that. And I hope you are realizing you are leaking
memory all over the place, and the design would become much simpler by
using std::set<node>.

BEst regards
Paavo