Compilare: main.cpp: In function 'int main()': main.cpp:15:13: warning: array subscript has type 'char' [-Wchar-subscripts] nr[c] = 0; ^ main.cpp:22:17: warning: array subscript has type 'char' [-Wchar-subscripts] nr[c]++; ^ main.cpp:32:32: warning: array subscript has type 'char' [-Wchar-subscripts] for(int i = 0; i < nr[c]; ++i) ^ main.cpp:36:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < s.size(); ++i) ~~^~~~~~~~~~