Compilare: main.cpp: In function 'void read(int&, int&, int&, std::vector<std::vector<int> >&)': main.cpp:10:34: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d %d", &n, &m, &s); ^ main.cpp:17:41: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d", &source, &target); ^ main.cpp: In function 'int main()': main.cpp:46:34: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("bfs.in", "r", stdin); ^ main.cpp:47:36: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("bfs.out", "w", stdout); ^