Compilare: user.cpp: In function ‘void BFS(int)’: user.cpp:45:38: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < v[n].size(); i++) ^ user.cpp: In function ‘void Back(int)’: user.cpp:71:38: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < v[n].size(); i++) ^ user.cpp: In function ‘int main()’: user.cpp:85:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("graf.in", "r", stdin); ^ user.cpp:86:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("graf.out", "w", stdout); ^ user.cpp:88:38: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d%d%d", &n, &m, &x, &y); ^ user.cpp:92:34: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d", &a, &b); ^