shortest path problem,I want to write constraints in closed form

Question

the constraints in the photo ,I need to translate to the closed-form I don't know how can I do this. Can you help?

I need to write the mod file and dat file in Cplex for this problem

Answer 1

In OPL to get the shortest path you could use:

.mod

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};
int st=1; // start
int en=8; // end

dvar int obj; // distance
dvar boolean x[edges]; // do we use that edge ?

minimize obj;

subject to
{
obj==sum(e in edges) x[e]*e.weight;

forall(i in nodes)
    sum(e in edges:e.o==i) x[e]
    -sum(e in edges:e.d==i) x[e]    
    ==
    ((i==st)?1:((i==en)?(-1):0));
}

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

execute
{
writeln(shortestPath);
}

.dat

edges=
{
<1,2,9>,
<1,3,9>,
<1,4,8>,
<1,10,18>,
<2,3,3>,
<2,6,6>,
<3,4,9>,
<3,5,2>,
<3,6,2>,
<4,5,8>,
<4,7,7>,
<4,9,9>,
<4,10,10>,
<5,6,2>,
<5,7,9>,
<6,7,9>,
<7,8,4>,
<7,9,5>,
<8,9,1>,
<8,10,4>,
<9,10,3>,
};

whicg gives

{<1 4 8> <4 7 7> <7 8 4>}