/in/foo.cc: In member function 'void Dijstra::dijstra(int)':
/in/foo.cc:97:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (int i = 0; i < G[target].size(); i++) //得到新的点，将新的点的边加入到优先队列中
                   ~~^~~~~~~~~~~~~~~~~~