Compilare: user.cpp: In function ‘void can_transform(std::string, std::string)’: user.cpp:31:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (n != b.length()) { ^ user.cpp:38:23: warning: array subscript has type ‘char’ [-Wchar-subscripts] if (modified[x] == 0) { ^ user.cpp:39:23: warning: array subscript has type ‘char’ [-Wchar-subscripts] modified[x] = b.at(i); ^ user.cpp:42:27: warning: array subscript has type ‘char’ [-Wchar-subscripts] if (modified[x] == b.at(i)) { ^