Abstract
It is well known that there exist efficient algorithms for the ordinary shortest path problem. In this study, we discuss a class of shortest path problems with task precedence constraings. Suppose that we use a vehicle to deliver some parcles from nodes u_1 and u_2 to nodes u_1 and u_2 respectively. THe node u_1 must be servcied before u_1 and the nodeu_2 before u_2,Nomura-Nakai[7]〜[9]ave discussed various types of vehicle routing problems Their problems are regarded as special cases of our shortest path problem. Finally, it is shown that the problem is NP-complete.
