Compilare: user.cpp: In function ‘int main()’: user.cpp:15:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0;i<strlen(ch);i++) ^ user.cpp:17:16: warning: array subscript has type ‘char’ [-Wchar-subscripts] v[ch[i]]++; ^ user.cpp:18:20: warning: array subscript has type ‘char’ [-Wchar-subscripts] if (v[ch[i]]>1) ^