/in/foo.cc: In function 'int AC::insert(int, char)':
/in/foo.cc:32:18: warning: array subscript has type 'char' [-Wchar-subscripts]
   if (!T[p].son[c]){
                  ^
/in/foo.cc:34:21: warning: array subscript has type 'char' [-Wchar-subscripts]
    return T[p].son[c]=tot;
                     ^
/in/foo.cc:36:25: warning: array subscript has type 'char' [-Wchar-subscripts]
   else return T[p].son[c];
                         ^