使用push-relabel方法求解最大流问题，是国外的一个研究机构编写的，速度很快。-This is an efficient implementation of the push-relabel method.

See

　Goldberg and Tarjan, "A New Approach to the Maximum Flow Problem,"

　J. ACM Vol. 35, 921--940, 1988

and

　Cherkassky and Goldberg, "On Implementing Push-Relabel Method for the

　Maximum Flow Problem," Proc. IPCO-4, 157--171, 1995.