Compilare: user.cpp: In function ‘void Read()’: user.cpp:26:9: warning: unused variable ‘c’ [-Wunused-variable] char c; ^ user.cpp: In function ‘void Do()’: user.cpp:40:26: warning: array subscript has type ‘char’ [-Wchar-subscripts] if(s[d.back()]==Complement(s[i])) ^ user.cpp:42:23: warning: array subscript has type ‘char’ [-Wchar-subscripts] a[d.back()]=1; ^ user.cpp:39:13: warning: suggest explicit braces to avoid ambiguous ‘else’ [-Wparentheses] { if(!d.empty()) ^ user.cpp: In function ‘char Complement(char)’: user.cpp:20:1: warning: control reaches end of non-void function [-Wreturn-type] } ^