/in/foo.cc: In function 'void DFS1(int)':
/in/foo.cc:39:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
      for(int k=0;k<g1[i].size();k++)
                  ~^~~~~~~~~~~~~
/in/foo.cc: In function 'void DFS2(int, int)':
/in/foo.cc:47:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int k=0;k<g2[i].size();k++)
                 ~^~~~~~~~~~~~~
/in/foo.cc: In function 'void suodian()':
/in/foo.cc:74:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
      for(int k=0;k<g1[i].size();k++)
                  ~^~~~~~~~~~~~~