Compilare: main.cpp: In function 'int main()': main.cpp:25:32: warning: comparison of integer expressions of different signedness: 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare] 25 | if(v[j].size() - 1 < i) | ~~~~~~~~~~~~~~~~^~~ main.cpp:29:35: warning: array subscript has type 'char' [-Wchar-subscripts] 29 | fr[ind[v[j][i - 1]]][ind[v[j][i]]] ++; | ^ main.cpp:29:49: warning: array subscript has type 'char' [-Wchar-subscripts] 29 | fr[ind[v[j][i - 1]]][ind[v[j][i]]] ++; | ^ main.cpp:31:34: warning: array subscript has type 'char' [-Wchar-subscripts] 31 | fr[0][ind[v[j][i]]] ++; | ^