Compilare: user.cpp: In function ‘void DFS(int, int)’: user.cpp:20:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0; i<v[k].size(); ++i) ^ user.cpp: In function ‘void calc(int, int)’: user.cpp:33:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0; i<v[k].size(); ++i) ^ user.cpp: In function ‘int main()’: user.cpp:45:36: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen ("arb2.in", "r", stdin); ^ user.cpp:46:38: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen ("arb2.out", "w", stdout); ^ user.cpp:47:21: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf ("%d", &n); ^ user.cpp:51:53: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf ("%d%d%d%d", &x, &y, &E.dist, &E.cost); ^