/in/foo.cc: In function 'void BFS()':
/in/foo.cc:35:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int k=0;k<g[i].size();k++){
               ~^~~~~~~~~~~~
/in/foo.cc: In function 'void DFS(int)':
/in/foo.cc:54:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int k=0;k<g[i].size();k++){
              ~^~~~~~~~~~~~
/in/foo.cc: In function 'void BFS2()':
/in/foo.cc:71:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int k=0;k<g[i].size();k++){
               ~^~~~~~~~~~~~