source: lemon-0.x/src/demo/lp_demo.cc @ 1317:83f80464f111

#include<lemon/lp_glpk.h>
#include<lemon/graph_reader.h>
#include<lemon/list_graph.h>

using namespace lemon;

template<class G,class C>
double maxFlow(const G &g,const C &cap,typename G::Node s,typename G::Node t)
{
  LpGlpk lp;
  
  typedef G Graph;
  typedef typename G::Node Node;
  typedef typename G::NodeIt NodeIt;
  typedef typename G::Edge Edge;
  typedef typename G::EdgeIt EdgeIt;
  typedef typename G::OutEdgeIt OutEdgeIt;
  typedef typename G::InEdgeIt InEdgeIt;
  
  typename G::template EdgeMap<LpGlpk::Col> x(g);
  lp.addColSet(x);
  
  for(EdgeIt e(g);e!=INVALID;++e) {
    lp.colUpperBound(x[e],cap[e]);
    lp.colLowerBound(x[e],0);
  }

  for(NodeIt n(g);n!=INVALID;++n) if(n!=s&&n!=t) {
    LpGlpk::Expr ex;
    for(InEdgeIt  e(g,n);e!=INVALID;++e) ex+=x[e];
    for(OutEdgeIt e(g,n);e!=INVALID;++e) ex-=x[e];
    lp.addRow(ex==0);
  }
  {
    LpGlpk::Expr ex;
    for(InEdgeIt  e(g,t);e!=INVALID;++e) ex+=x[e];
    for(OutEdgeIt e(g,t);e!=INVALID;++e) ex-=x[e];
    lp.setObj(ex);
  }

  lp.solve();

  return 0;
}

int main() 
{
  LpGlpk lp_glpk;

  ListGraph g;
  ListGraph::Node s=g.addNode();
  ListGraph::Node t=g.addNode();

  ListGraph::EdgeMap<double> cap(g);
  
  GraphReader<ListGraph> reader(std::cin,g);
  reader.addEdgeMap("capacity",cap).run();
  
  maxFlow(g,cap,s,t);

}