Compilare: main.cpp: In function 'int main()': main.cpp:15:16: warning: array subscript has type 'char' [-Wchar-subscripts] fr[v[i]]++; ^ main.cpp:16:19: warning: array subscript has type 'char' [-Wchar-subscripts] if(fr[v[i]]==1){ ^ main.cpp:20:21: warning: array subscript has type 'char' [-Wchar-subscripts] fr[v[st]]--; ^ main.cpp:21:24: warning: array subscript has type 'char' [-Wchar-subscripts] if(fr[v[st]]==0) ^