Compilare: user.cpp: In function ‘void eraseEdge(int, int, int)’: user.cpp:49:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i <v[x].size(); i++) ^ user.cpp: In function ‘void read()’: user.cpp:19:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("johnie.in", "r", stdin); ^ user.cpp:21:27: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d", &N, &M); ^ user.cpp:23:31: 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:133:39: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("johnie.out", "w", stdout); ^