/in/foo.cc: In function 'int main()':
/in/foo.cc:63:16: warning: array subscript has type 'char' [-Wchar-subscripts]
      used[cur.c] = false;
                ^
/in/foo.cc:73:23: warning: array subscript has type 'char' [-Wchar-subscripts]
     if (used[bianliang]) {
                       ^
/in/foo.cc:97:19: warning: array subscript has type 'char' [-Wchar-subscripts]
     used[bianliang] = true;
                   ^