线性规划、对偶、费用流(Linear programming, duality, cost flow)
有时需新增变量 \(t=0\)，可以发现从 \(t\) 连出（入）的边等价于从 \(S\)（\(T\)）连出（入）。
Linear programming to duality
Cost flow model and its duality
Sometimes it is necessary to add a variable \ (t = 0 \), and it can be found that the edge connected out (in) from \ (t \) is equivalent to that connected out (in) from \ (s \) (\ (t \)).