foo.cc: In function 'int cc()':
foo.cc:9:10: warning: unused variable 'o' [-Wunused-variable]
  int d=0,o=0;
          ^
foo.cc: In function 'int main()':
foo.cc:71:7: warning: unused variable 'step' [-Wunused-variable]
   int step=1;
       ^~~~
foo.cc:52:8: warning: variable 'aa' set but not used [-Wunused-but-set-variable]
  int T,aa,bb;
        ^~
foo.cc:52:11: warning: variable 'bb' set but not used [-Wunused-but-set-variable]
  int T,aa,bb;
           ^~
foo.cc: In function 'void dfs(int, int)':
foo.cc:22:8: warning: 'y' may be used uninitialized in this function [-Wmaybe-uninitialized]
  int x,y;
        ^

自豪的采用jd5进行评测(github.com/masnn/jd5)