foo.cc: In function 'int bfs()':
foo.cc:47:1: warning: this 'if' clause does not guard... [-Wmisleading-indentation]
 if(next.x==ex && next.y==ey)return next.step; next.step;
 ^~
foo.cc:47:47: note: ...this statement, but the latter is misleadingly indented as if it were guarded by the 'if'
 if(next.x==ex && next.y==ey)return next.step; next.step;
                                               ^~~~
foo.cc:47:52: warning: statement has no effect [-Wunused-value]
 if(next.x==ex && next.y==ey)return next.step; next.step;
                                               ~~~~~^~~~
foo.cc: In function 'int main()':
foo.cc:63:6: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
 scanf("%d%d",&n,&m);
 ~~~~~^~~~~~~~~~~~~~
foo.cc:68:6: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
 scanf("%d",&data[i][j]);
 ~~~~~^~~~~~~~~~~~~~~~~~
foo.cc:71:6: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
 scanf("%d%d%d%d",&sx,&sy,&ex,&ey);
 ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~
foo.cc:73:6: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
 scanf("%c",&ch);
 ~~~~~^~~~~~~~~~
foo.cc:74:6: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
 scanf("%c",&ch);
 ~~~~~^~~~~~~~~~

自豪的采用HydroJudge(https://github.com/hydro-dev/Hydro)进行评测。