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:34:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (nr > 0 && i < rez.size() - 1 && rez[i] != el && rez[i - 1] != el) ~~^~~~~~~~~~~~~~~~