Coding MST (4) in CPLEX

Question

I'm trying to code MST4 in CPLEX, but because I'm new to code writing I have difficulty in doing it. I would really appreciate if anyone could help me. Thanks

Answer 1

In OPL tips and tricks see Minimum Spanning Tree

    tuple edge
    {
        key int o;
        key int d;
        int weight;
    }

    {edge} edges=...;

    {int} nodes={i.o | i in edges} union {i.d | i in edges};

    range r=1..-2+ftoi(pow(2,card(nodes)));
    {int} nodes2 [k in r] = {i | i in nodes: ((k div (ftoi(pow(2,(ord(nodes,i))))) mod 2) == 1)};

    dvar boolean x[edges];

    minimize sum (e in edges) x[e]*e.weight;
    subject to
    {
    sum(e in edges) x[e]==card(nodes)-1;

    // Subtour elimination constraints.
       
    forall(k in r)  // all subsets but empty and all
        sum(e in edges:(e.o in nodes2[k]) && (e.d in nodes2[k])) x[e]<=card(nodes2[k])-1;  
       
    }

    {edge} solution={e | e in edges : x[e]==1};

    execute
    {
    writeln("minimum spanning tree ",solution);
    }