Is there a possibility to create a lemon graph using a loop in C++?
My Problem:
- A database table (let's call it t_nodes) with column: node
- A database table (let's call it t_edges) with graph information: node1 | node2 | edgeScore
- More than 10000 entries
My desired outcome:
- A directed graph: e.g. N1 -> N2; N2 -> N3; N3 -> N1
My Question
Is it possible to use a loop for each entry within the
t_nodes
table to add a node to a graph- So far, I just found implementations where they add each node manually (see example below)
- Is there really no opportunity to use a loop to add nodes to a lemon graph?
How can I use a loop for all the relations mentioned in
t_edges
?
Thanks for your time and any help is greatly appreciated!
After having some free time over the weekend and spending some time on my bike I found the solution :)
My Solution:
It seems, that lemon did not offer the possibility to support additional information to the edges within the graph. Therefore I just created a additional vector for storing this information. However, for some purposes it may be more wise to use a hashmap for accessing the nodes.
Have a look at the developed example script (very trivial ;) )
Lemon C++-Code example (reference: http://lemon.cs.elte.hu/pub/tutorial/a00022.html):
/* -*- mode: C++; indent-tabs-mode: nil; -*-
*
* This file is a part of LEMON, a generic C++ optimization library.
*
* Copyright (C) 2003-2010
* Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
* (Egervary Research Group on Combinatorial Optimization, EGRES).
*
* Permission to use, modify and distribute this software is granted
* provided that this copyright notice appears in all copies. For
* precise terms see the accompanying LICENSE file.
*
* This software is provided "AS IS" with no warranty of any kind,
* express or implied, and with no claim as to its suitability for any
* purpose.
*
*/
#include <iostream>
#include <lemon/list_graph.h>
using namespace lemon;
using namespace std;
int main()
{
ListDigraph g;
ListDigraph::Node u = g.addNode();
ListDigraph::Node v = g.addNode();
ListDigraph::Arc a = g.addArc(u, v);
cout << "Hello World! This is LEMON library here." << endl;
cout << "We have a directed graph with " << countNodes(g) << " nodes "
<< "and " << countArcs(g) << " arc." << endl;
return 0;
// Further development
ListDigraph graph;
vector <string> name;
name.push_back("A");
name.push_back("B");
name.push_back("C");
for (unsigned int n=0; n<name.size(); n++) {
ListDigraph::Node node = graph.addNode();
lemon_node_vector[n].id = n;
lemon_node_vector[n].name = name[n];
}
}
Of course, you can execute AddNode and AddArc in a loop. Or in a recursive function. Or in any other way you want to.
Did you try it? Was there some error?