foo.cpp: In function 'void dfs0(int, int)':
foo.cpp:23:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<g0[v].size();i++)
              ~^~~~~~~~~~~~~
foo.cpp: In function 'void dfs1(int, int)':
foo.cpp:51:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<g[v].size();i++)
              ~^~~~~~~~~~~~
foo.cpp: In function 'void dfs2(int, int)':
foo.cpp:64:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<g[v].size();i++)
              ~^~~~~~~~~~~~
foo.cpp: In function 'int main()':
foo.cpp:121:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int j=0;j<g0[i].size();j++)
               ~^~~~~~~~~~~~~