Compilare: user.cpp: In function ‘int main()’: user.cpp:14:15: warning: array subscript has type ‘char’ [-Wchar-subscripts] x[s[i]]=(char)(i+'a'); ^ user.cpp:15:24: warning: array subscript has type ‘char’ [-Wchar-subscripts] y[(char)(i+'a')]=s[i]; ^ user.cpp:21:30: warning: array subscript has type ‘char’ [-Wchar-subscripts] S[i][j]=x[S[i][j]]; ^ user.cpp:35:30: warning: array subscript has type ‘char’ [-Wchar-subscripts] S[i][j]=y[S[i][j]]; ^