Compilare: user.cpp: In function ‘void makeprefix()’: user.cpp:10:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i = 1; i < A.size(); i++) ^ user.cpp: In function ‘int main()’: user.cpp:27:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i = 1; i < B.length(); i++) ^ user.cpp:33:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (k == A.length() - 1) ^