数学建模 TSP(旅行商问题) Lingo求解

model:
sets:
cities/../:level;
link(cities, cities): distance, x;   !距离矩阵;
endsets
data:
distance =                                                     
                                            ;
enddata
n = @size(cities);
!目标函数;
min=@sum(link:distance * x);
@For(cities(k):
     !进入城市k;
     @sum(cities(i) | i #ne# k: x(i,k)) = ;
     !离开城市k;
     @sum(cities(j) | j #ne# k: x(k,j)) = ;
    );
    !保证不出现子圈;
    @for(cities(i) | i #gt# :
    @for(cities(j) | j #gt#  #and# i#ne#j:
        level(i)-level(j) + n*x(i,j) <= n-);
     );
    !限制u的范围以加速模型的求解，保证所加限制并不排除掉TSP问题的最优解;
    @for(cities(i) | i #gt# : level(i) <= n-);
    !定义x为 \1变量;
    @for(link:@bin(x));
end