Compilare: user.cpp: In function ‘int main()’: user.cpp:20:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<strlen(s);i++) ^ user.cpp:26:23: warning: array subscript has type ‘char’ [-Wchar-subscripts] if(v[c]==0) ^ user.cpp:28:24: warning: array subscript has type ‘char’ [-Wchar-subscripts] v[c]=c1; ^ user.cpp:32:27: warning: array subscript has type ‘char’ [-Wchar-subscripts] if(v[c]!=c1) ^