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find min/max values in stl container

Posted on 2001-09-11
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Last Modified: 2012-08-14
Hi,
I have following data structure:
std::vector<Vertex3D*> ArrayVertex;
which is the vector of pointers.
Class Vertex3D contains some value of type double:
double curv;
what I need is to find min/max curv in my ArrayVertex fastest way using STL.
Thanks
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Question by:borlip
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4 Comments
 
LVL 4

Expert Comment

by:IainHere
ID: 6474475
If vertex3D has comparison operators > and < that return based on curv, then you can simply use min_element and max_element.

minEl = min_element(ArrayVertex.begin(), ArrayVertex.end);

If it doesn't (probably the case) you'll have to define a function that does the comparison for you.  Something like

bool vertex_compare( const Vertex3D& a_, const Vertex3D& b_ )
  {
  if (a_.curv > b_.curv)
     return true;
 
  return false;
  }

and then use it:

minEl = min_element(ArrayVertex.begin(), ArrayVertex.end, vertex_compare);
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LVL 30

Expert Comment

by:Axter
ID: 6474480
50 points are assigned to an easy question.
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LVL 1

Expert Comment

by:alex_r
ID: 6474496
I would NOT recommend doing the following:
minEl = min_element(ArrayVertex.begin(), ArrayVertex.end);

min_element going to compare pointers of type Vertex3D, not the objects of type Vertex3D.

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LVL 1

Accepted Solution

by:
alex_r earned 28 total points
ID: 6474505
I think borlip has to use min_element version with 3 arguments and the vertext_compare should look like:

bool vertex_compare( const Vertex3D* a_, const Vertex3D* b_ )
...
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