Compilare: user.cpp: In function ‘void Evaluate()’: user.cpp:42:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<=S.size();i++) ^ user.cpp: In function ‘int main()’: user.cpp:82:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<=S.size();i++) ^ user.cpp:105:12: warning: array subscript has type ‘char’ [-Wchar-subscripts] x[k]=!x[k]; ^ user.cpp:105:18: warning: array subscript has type ‘char’ [-Wchar-subscripts] x[k]=!x[k]; ^