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#include<lemon/graph_reader.h>
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alpar@1361
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#include<lemon/list_graph.h>
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alpar@1361
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alpar@1381
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#ifdef HAVE_GLPK
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#include <lemon/lp_glpk.h>
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#elif HAVE_CPLEX
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#include <lemon/lp_cplex.h>
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#endif
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using namespace lemon;
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#ifdef HAVE_GLPK
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typedef LpGlpk LpDefault;
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#elif HAVE_CPLEX
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typedef LpCplex LpDefault;
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#endif
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template<class G,class C>
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double maxFlow(const G &g,const C &cap,typename G::Node s,typename G::Node t)
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{
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LpDefault lp;
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typedef G Graph;
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typedef typename G::Node Node;
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typedef typename G::NodeIt NodeIt;
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typedef typename G::Edge Edge;
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typedef typename G::EdgeIt EdgeIt;
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typedef typename G::OutEdgeIt OutEdgeIt;
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typedef typename G::InEdgeIt InEdgeIt;
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typename G::template EdgeMap<LpDefault::Col> x(g);
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lp.addColSet(x);
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for(EdgeIt e(g);e!=INVALID;++e) {
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lp.colUpperBound(x[e],cap[e]);
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lp.colLowerBound(x[e],0);
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}
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for(NodeIt n(g);n!=INVALID;++n) if(n!=s&&n!=t) {
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LpDefault::Expr ex;
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for(InEdgeIt e(g,n);e!=INVALID;++e) ex+=x[e];
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for(OutEdgeIt e(g,n);e!=INVALID;++e) ex-=x[e];
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lp.addRow(ex==0);
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}
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{
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LpDefault::Expr ex;
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for(InEdgeIt e(g,t);e!=INVALID;++e) ex+=x[e];
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for(OutEdgeIt e(g,t);e!=INVALID;++e) ex-=x[e];
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lp.setObj(ex);
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}
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lp.max();
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#ifdef HAVE_GLPK
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lp.presolver(true);
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lp.messageLevel(3);
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#endif
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lp.solve();
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return lp.primalValue();
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}
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int main()
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{
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ListGraph g;
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ListGraph::Node s;
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ListGraph::Node t;
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ListGraph::EdgeMap<double> cap(g);
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GraphReader<ListGraph> reader(std::cin,g);
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reader.addNode("source",s).addNode("target",t)
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.addEdgeMap("capacity",cap).run();
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// std::ifstream file("../test/preflow_");
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// readDimacs(file, g, cap, s, t);
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std::cout << "Max flow value = " << maxFlow(g,cap,s,t) << std::endl;
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}
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