how to compare lists of structures using iterator?

Question

I have a structure.

struct Vertex
{
       list<Vertex> adj;
       unsigned short distance; // zero or infinity
       bool known;

};

I want to compare distance in the elements of list type vertex; any idea???

Vertex findMin(list<Vertex> &adj)
{
       Vertex min;
       for(list<Vertex>::iterator it = adj.begin(); it != adj.end(); it++){
                 // if(it->distance < (adj.next())->distance){

                  //}

       return min;
}

I am using this function to return min vertex on the basis of distance property

Answer 1

Vertex findMin(const list<Vertex> &adj)
{
  if(adj.empty())
    throw(0); // cannot find minimum of an empty list;

  list<Vertex>::const_iterator bestVertex = adj.begin();
  unsigned short minDistance = bestVertex->distance;

  for(list<Vertex>::const_iterator itr=adj.begin(); itr!=adj.end(); ++itr)
    if(itr->distance < minDistance)
      {
        bestVertex = itr;
        minDistance = bestVertex->distance;
      }

  return *bestVertex;
}

Answer 2

Use the std::min_element algorithm. Here is pre-C++11 code:

bool isDistanceLess(const Vertex& v1, const Vertex& v2)
{  return v1.distance < v2.distance; }

Vertex findMin(const std::list<Vertex>& adj)
{ return *std::min_element(adj.begin(), adj.end(), isDistanceLess); }

Here is the C++11 version:

Vertex findMin(const std::list<Vertex>& adj)
{ return *std::min_element(adj.begin(), adj.end(), [](const Vertex& v1, const Vertex& v2) { return v1.distance < v2.distance; })); }