foo.cc: In function 'void work()':
foo.cc:114:19: error: 'id' was not declared in this scope
    for(int j=dead[id];j;j=d[j].nex)
                   ^~
foo.cc:114:19: note: suggested alternative: 'i'
    for(int j=dead[id];j;j=d[j].nex)
                   ^~
                   i
foo.cc:101:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d",&m);int x,y;
  ~~~~~^~~~~~~~~
foo.cc:104:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d%d",&x,&y);add2(y,x);
   ~~~~~^~~~~~~~~~~~~~
foo.cc: In function 'int main()':
foo.cc:132:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%s",s);
  ~~~~~^~~~~~~~

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