[lingo] find the minimum connection diagram of seven cities to minimize the price of natural gas pipelines

Catalog

1、 Problem description

 2、 problem solving

---

1、 Problem description

 2、 problem solving

model:
sets:
cities/A,B1,B2,C1,C2,C3,D/;
roads(cities,cities)/A B1,A B2,B1 C1,B1 C2,B1 C3,B2 C1,
B2 C2,B2 C3,C1 D,C2 D,C3 D/:w,x;
endsets
data:
w=2 4 3 3 1 2 3 1 1 3 4;
enddata
[email protected](cities); ! Number of cities ;
[email protected](roads:w*x);
@for(cities(i)|i #ne#1 #and# i #ne#n:
@sum(roads(i,j):x(i,j))[email protected](roads(j,i):x(j,i)));
@sum(roads(i,j)|i #eq#1:x(i,j))=1;
@sum(roads(i,j)|j #eq#n:x(i,j))=1;
end