View Compilation Error

0_0_21595712_19904.cpp:72:15: error: stray '#' in program
   return c - 'a';
               ^
0_0_21595712_19904.cpp:72:21: error: stray '#' in program
   return c - 'a';
                     ^
0_0_21595712_19904.cpp: In member function 'int Aho_Corasick::idx(char)':
0_0_21595712_19904.cpp:72:16: error: lvalue required as unary '&' operand
   return c - 'a';
                ^
0_0_21595712_19904.cpp:72:19: error: 'a' was not declared in this scope
   return c - 'a';
                   ^