Compilare: user.cpp: In function ‘int main()’: user.cpp:57:46: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int u = 0; u <= v1.size() - 1; ++u) ^ user.cpp:59:46: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int u = 0; u <= v2.size() - 1; ++u) ^ user.cpp:63:46: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int u = 0; u <= v1.size() - 1; ++u) ^ user.cpp:65:46: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int u = 0; u <= v2.size() - 1; ++u) ^ user.cpp:69:46: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int u = 0; u <= v1.size() - 1; ++u) ^ user.cpp:71:46: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int u = 0; u <= v2.size() - 1; ++u) ^ user.cpp: In function ‘void write_output()’: user.cpp:35:18: warning: ‘j’ may be used uninitialized in this function [-Wmaybe-uninitialized] fout << j; ^