Compilare: main.cpp: In function 'int main()': main.cpp:10:12: warning: array subscript has type 'char' [-Wchar-subscripts] freq[it]++; ^ main.cpp:12:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 1; i <= s.size(); i++) { ~~^~~~~~~~~~~ main.cpp:16:17: warning: array subscript has type 'char' [-Wchar-subscripts] if (freq[c]) best_lett = c; ^ main.cpp:17:17: warning: array subscript has type 'char' [-Wchar-subscripts] if (freq[c] == (s.size() - i + 1) / 2 + 1) { ^ main.cpp:17:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (freq[c] == (s.size() - i + 1) / 2 + 1) { ~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~ main.cpp:22:19: warning: array subscript has type 'char' [-Wchar-subscripts] freq[best_lett]--; ^ main.cpp:13:10: warning: 'best_lett' may be used uninitialized in this function [-Wmaybe-uninitialized] char best_lett; ^~~~~~~~~