Compilare: user.cpp: In function ‘int main()’: user.cpp:25:14: warning: array subscript has type ‘char’ [-Wchar-subscripts] ap[b[i]].push_back(i); ^ user.cpp:28:25: warning: array subscript has type ‘char’ [-Wchar-subscripts] for (j=0;j<ap[a[i]].size();j++) ^ user.cpp:28:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (j=0;j<ap[a[i]].size();j++) ^ user.cpp:30:20: warning: array subscript has type ‘char’ [-Wchar-subscripts] k=ap[a[i]][j]; ^