/in/foo.cc: In function 'void pre()':
/in/foo.cc:9:8: warning: unused variable 'j' [-Wunused-variable]
  int i,j;
        ^
/in/foo.cc: In function 'void dfs()':
/in/foo.cc:32:13: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (j=0;j<e[i].size();j++){
            ~^~~~~~~~~~~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:44:2: warning: this 'for' clause does not guard... [-Wmisleading-indentation]
  for (i=1;i<n;i++) printf("%d ",num[i]);printf("%d\n",num[n]);
  ^~~
/in/foo.cc:44:41: note: ...this statement, but the latter is misleadingly indented as if it is guarded by the 'for'
  for (i=1;i<n;i++) printf("%d ",num[i]);printf("%d\n",num[n]);
                                         ^~~~~~
/in/foo.cc:40:8: warning: unused variable 'j' [-Wunused-variable]
  int i,j;
        ^