gas pipeline game

题目地址：
http://www.1point3acres.com/bbs/forum.php?mod=viewthread&tid=201986&extra=page%3D1%26filter%3Dsortid%26sortid%3D311%26searchoption%5B3046%5D%5Bvalue%5D%3D1%26searchoption%5B3046%5D%5Btype%5D%3Dradio%26sortid%3D311

题目和解题思路：