Compilare: user.cpp: In function ‘int main()’: user.cpp:13:35: warning: array subscript has type ‘char’ [-Wchar-subscripts] if (c[i] != ch) if (s[c[i]] && s[c[i]] != ch) return fo << "NU\n",0;else s[c[i]] = ch; ^ user.cpp:13:46: warning: array subscript has type ‘char’ [-Wchar-subscripts] if (c[i] != ch) if (s[c[i]] && s[c[i]] != ch) return fo << "NU\n",0;else s[c[i]] = ch; ^ user.cpp:13:88: warning: array subscript has type ‘char’ [-Wchar-subscripts] if (c[i] != ch) if (s[c[i]] && s[c[i]] != ch) return fo << "NU\n",0;else s[c[i]] = ch; ^ user.cpp:13:12: warning: suggest explicit braces to avoid ambiguous ‘else’ [-Wparentheses] if (c[i] != ch) if (s[c[i]] && s[c[i]] != ch) return fo << "NU\n",0;else s[c[i]] = ch; ^ user.cpp:16:85: warning: array subscript has type ‘char’ [-Wchar-subscripts] for (int i='a';i<='z';++i) if (s[i]) fo << char(i) << ' ' << s[i] << '\n',s[s[i]] = 0; ^