Compilare: user.cpp: In function ‘void BFS(int)’: user.cpp:29:38: 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:50:38: 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:63:35: 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:64:37: 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:66:38: 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:70:34: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d", &a, &b); ^