/in/foo.cc: In function 'bool dfs(int)':
/in/foo.cc:17:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i = 0; i < strlen(op[t]); i++)
                  ~~^~~~~~~~~~~~~~~
/in/foo.cc:38:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^