foo.cc: In function 'void BFS()':
foo.cc:22:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int k = 0; k < ep.size(); k++)
                  ~~^~~~~~~~~~~
foo.cc: In function 'int main()':
foo.cc:53:14: warning: 'char* gets(char*)' is deprecated [-Wdeprecated-declarations]
   gets(mat[i]);
              ^
In file included from /usr/include/c++/7/cstdio:42:0,
                 from foo.cc:1:
/usr/include/stdio.h:638:14: note: declared here
 extern char *gets (char *__s) __wur __attribute_deprecated__;
              ^~~~
foo.cc:50:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d%d", &W, &H);
  ~~~~~^~~~~~~~~~~~~~~~
foo.cc:53:7: warning: ignoring return value of 'char* gets(char*)', declared with attribute warn_unused_result [-Wunused-result]
   gets(mat[i]);
   ~~~~^~~~~~~~
/tmp/ccRl0gfk.o: In function `main':
foo.cc:(.text.startup+0x66): warning: the `gets' function is dangerous and should not be used.

自豪的采用 HydroJudger 进行评测(github.com/hydro-dev/HydroJudger)

{"receive":"2020-05-23T10:13:43.188Z","handle":"2020-05-23T10:13:43.189Z","cache_start":"2020-05-23T10:13:43.195Z","read_cases":"2020-05-23T10:13:43.332Z","judge":"2020-05-23T10:13:43.333Z","done":"2020-05-23T10:13:43.947Z"}