foo.cc: In function 'void spfa(int)':
foo.cc:25:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for(int i=0;i<a[x].to.size();i++){
                     ~^~~~~~~~~~~~~~~
foo.cc: In function 'int main()':
foo.cc:36:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d%d%d%d%d",&n,&k,&m,&s,&t);
     ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
foo.cc:37:21: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     For(i,1,n) scanf("%d",&c[i]);
                ~~~~~^~~~~~~~~~~~
foo.cc:38:32: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     For(i,1,k) For(j,1,k) scanf("%d",&map[i][j]);
                           ~~~~~^~~~~~~~~~~~~~~~~
foo.cc:41:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%d%d%d",&x,&y,&z);
         ~~~~~^~~~~~~~~~~~~~~~~~~

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