Compilare: user.cpp: In function ‘int main()’: user.cpp:19:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<strlen(s);i++) ^ user.cpp:25:19: warning: array subscript has type ‘char’ [-Wchar-subscripts] if(v[c]==0) ^ user.cpp:27:20: warning: array subscript has type ‘char’ [-Wchar-subscripts] v[c]=c1; ^ user.cpp:31:23: warning: array subscript has type ‘char’ [-Wchar-subscripts] if(v[c]!=c1) ^