Compilare: user.cpp: In function ‘int main()’: user.cpp:17:20: warning: array subscript has type ‘char’ [-Wchar-subscripts] if (!v[s[i]]) {stiva[++vf]=s[i];v[s[i]]=1;nr++;} ^ user.cpp:17:47: warning: array subscript has type ‘char’ [-Wchar-subscripts] if (!v[s[i]]) {stiva[++vf]=s[i];v[s[i]]=1;nr++;} ^ user.cpp:19:63: warning: array subscript has type ‘char’ [-Wchar-subscripts] while (stiva[vf]!=s[i] && vf!=0) {vf--;nr++;v[s[i]]=0;} ^