Compilare: main.cpp: In function 'int main()': main.cpp:25:13: warning: array subscript has type 'char' [-Wchar-subscripts] a[it]++; ^ main.cpp:40:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < s.size(); i++) { ~~^~~~~~~~~~ main.cpp:53:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (dr == s.size()) dr = 0; ~~~^~~~~~~~~~~ main.cpp:66:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 1; i + 1 < s.size(); i++) { ~~~~~~^~~~~~~~~~ main.cpp:103:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (dr == s.size()) dr = 0; ~~~^~~~~~~~~~~