Compilare: main.cpp: In function 'int main()': main.cpp:37:14: warning: array subscript has type 'char' [-Wchar-subscripts] 37 | f[s[i]]++; | ~~~^ main.cpp:42:15: warning: array subscript has type 'char' [-Wchar-subscripts] 42 | if (f[i] != 0) | ^ main.cpp:44:19: warning: array subscript has type 'char' [-Wchar-subscripts] 44 | if (f[i] > 1) | ^