/in/foo.cc: In function 'int BFS()':
/in/foo.cc:39:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for(int ka=0;ka<g[a].size();ka++){  //卡车向前一步 走到na 
                      ~~^~~~~~~~~~~~
/in/foo.cc:41:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
             for(int kb=0;kb<g[b].size();kb++){ //检查团向前一步 走到nb 
                          ~~^~~~~~~~~~~~
/in/foo.cc:36:17: warning: unused variable 'd' [-Wunused-variable]
         int a,b,d;
                 ^