严格的数学模型-Flow Network A.flow network G=(V,E)is adirected graph in which each edge (u,v)EE has a nonnegative capacity c(u,v)=0.We further require that if E contains an edge (u,v),then there is no edge (v,u)in the reverse direction.(We shall see shortly how to work around this restriction.)If (u,v)E,then for convenience we define c(u,v)=0,and we disallow self-loops.We distinguish two vertices in a flow network:a source s and a sink t.For convenience,we assume that each vertex lies on some path from the source to the sink.That is,for each vertex v eV, the flow network contains a path svt.The graph is therefore connected and,since each vertex other than s has at least one entering edge,EV-1. 2020/12/08严格的数学模型- Flow Network 2020/12/08 7