Compilare: main.cpp: In function 'int main()': main.cpp:11:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < s.size(); ++i) ~~^~~~~~~~~~ main.cpp:12:18: warning: array subscript has type 'char' [-Wchar-subscripts] ++fv[s[i]]; ^ main.cpp:13:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < s.size(); ++i) { ~~^~~~~~~~~~ main.cpp:20:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (maxap > (s.size() - i) / 2 + 1) { ~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~