Building a Directed Graph from a file - c++

Question

I need to read in a file and build a directed graph from it. I am working in C++. The file looks like this:
SFA SLC 700 59
SFO LV 420 39
LAX LV 231 23
LV SLC 362 29
LAX SFO 344 39
LAX SLC 581 57
SFA SFO 679 67
SFO SLC 605 19
PHX DEN 586 65
LV PHX 256 21
DEN SFA 1026 72
DEN LAX 844 69
SLC DEN 379 49
SLC SJC 585 29
SJC SFO 51 19
The first line means there is a flight from SFA to SLC which is 700 miles and cost $59 and each line follows this formula. I am having a really hard time figuring out a good way to do this. Any help would be so much appreciated. Thank you in advance.

Answer 1

I suggest using Lemon, see tutorial: http://lemon.cs.elte.hu/pub/tutorial/a00011.html
Generally speaking you separate structure (the graph) and the data. So in case of lemon you would read each line, split it into 4 fields (delimiter being the whitespace). During the read of the file you should also maintain the hash or map (e.g. std::unordered_map) to quickly lookup destinations already in the graph (or use graph API to find them but that would be slower).
So:
ListDigraph g;
ListDigraph::NodeMap<std::string> gDestinations(g);
ListDigraph::ArcMap<int> gCosts(g);
ListDigraph::ArcMap<int> gDistances(g);
std::unordered_map<std::string, ListDigraph::Node> destinations;
And then for each row:
//first read the line, split it be whitespace into 4 fields, e.g. into these
std::string destFrom, destTo;
int distance, cost;
//first the structure
auto itFrom = destinations.insert(destFrom, g.addNode()).first; //dest is the first or second field in your file
auto itTo = destinations.insert(destTo, g.addNode()).first; //dest is the first or second field in your file
ListDigraph::Arc route = g.addArc(*itFrom, *itTo);
//then the data
gDestinations[*itFrom] = destFrom; //well this could be done once if the place exists already, this s for brevity
gDestinations[*itTo] = destTo; //dtto
gDistances[route] = distance; //distance is the third field
gCosts[route] = cost; //cost is the fourth field
And that is it. See the tutorial and Lemon documentation how to use graph algorithms and manipulate the graph etc.