Compilare: main.cpp: In function 'int main()': main.cpp:12:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < b.size(); ++i) { ~~^~~~~~~~~~ main.cpp:13:20: warning: array subscript has type 'char' [-Wchar-subscripts] if (fv[b[i]] == 0) ^ main.cpp:15:18: warning: array subscript has type 'char' [-Wchar-subscripts] ++fv[b[i]]; ^ main.cpp:16:19: warning: array subscript has type 'char' [-Wchar-subscripts] ++fv2[b[i]]; ^ main.cpp:17:16: warning: array subscript has type 'char' [-Wchar-subscripts] ok[b[i]] = true; ^ main.cpp:20:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < a.size(); ++i) { ~~^~~~~~~~~~ main.cpp:21:21: warning: array subscript has type 'char' [-Wchar-subscripts] if (!ok[a[i]] || fv2[a[i]] == 0) ^ main.cpp:21:34: warning: array subscript has type 'char' [-Wchar-subscripts] if (!ok[a[i]] || fv2[a[i]] == 0) ^ main.cpp:23:19: warning: array subscript has type 'char' [-Wchar-subscripts] --fv2[a[i]]; ^ main.cpp:25:21: warning: array subscript has type 'char' [-Wchar-subscripts] if (fv2[a[i]] == 0) ^