Compilare: main.cpp: In function 'int main()': main.cpp:16:15: warning: array subscript has type 'char' [-Wchar-subscripts] f[s[i]]++; ^ main.cpp:17:19: warning: array subscript has type 'char' [-Wchar-subscripts] if (f[s[i]] == 1) ^ main.cpp:20:21: warning: array subscript has type 'char' [-Wchar-subscripts] f[ s[p] ]--; ^ main.cpp:21:23: warning: array subscript has type 'char' [-Wchar-subscripts] if (f[s[p]] == 0) ^