Compilare: user.cpp: In function ‘int dfs(int)’: user.cpp:43:1: warning: no return statement in function returning non-void [-Wreturn-type] } ^ user.cpp: In function ‘void write()’: user.cpp:47:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < r.size(); ++i) ^ user.cpp: In function ‘void read()’: user.cpp:26:40: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen ("sortaret.in", "r", stdin); ^ user.cpp:27:27: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf ("%d%d", &n, &m); ^ user.cpp:30:31: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf ("%d%d", &x, &y); ^ user.cpp: In function ‘void write()’: user.cpp:46:42: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen ("sortaret.out", "w", stdout); ^