运筹学 Operations Research f(s)=f(s\s)=∑f(s,v (S,")∈(s,s) ()=f(V,1)=∑ (v,D)∈(t},t) 可行流( feasible flow): (1)va∈A,有0≤f(a)≤c(a) (2)f(s)=f(t);vv∈l,有f(s)=f(t) 流值( flow value):vakf)=f*(s)=f() 2021/2/20 62021/2/20 6 运 筹 学 Operations Research   + = = ( , ) ( , \{ }) ( ) ( , \{ }) ( , ) s v s V s j j f s f s V s f s v    − = = ( , ) ( \{ }, ) ( ) ( \{ }, ) ( , ) v t V t t j j f t f V t t f v t 可行流（feasible flow）： (1)a A，有0  f (a)  c(a) (2) f (s) f (t) v I f (s) f (t) + − + − = ；  ，有 = 流值（flow value）： val( f ) f (s) f (t) + −  = =