foo.cc: In function 'int main()':
foo.cc:42:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<s.size();i++){
              ~^~~~~~~~~
foo.cc:43:13: warning: array subscript has type 'char' [-Wchar-subscripts]
   if(bd[s[i]]){
             ^
foo.cc:44:17: warning: array subscript has type 'char' [-Wchar-subscripts]
    if(!bd[s[i-1]])hz+='.';
                 ^
foo.cc:45:14: warning: array subscript has type 'char' [-Wchar-subscripts]
    if(bd[s[i]]==1)st2.push(s[i]);
              ^
foo.cc:46:19: warning: array subscript has type 'char' [-Wchar-subscripts]
    else if(bd[s[i]]==5){
                   ^
foo.cc:56:38: warning: array subscript has type 'char' [-Wchar-subscripts]
      while(!st2.empty()&&bd[st2.top()]>=bd[s[i]]){
                                      ^
foo.cc:56:48: warning: array subscript has type 'char' [-Wchar-subscripts]
      while(!st2.empty()&&bd[st2.top()]>=bd[s[i]]){
                                                ^
foo.cc:66:22: warning: array subscript has type 'char' [-Wchar-subscripts]
  if(!bd[s[s.size()-1]])hz+='.';
                      ^
foo.cc:73:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<hz.size();i++){
              ~^~~~~~~~~~

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