Compilare: user.cpp: In function ‘int main()’: user.cpp:26:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("dijkstra.in","r",stdin); ^ user.cpp:27:39: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("dijkstra.out","w",stdout); ^ user.cpp:28:26: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d", &n, &m); ^ user.cpp:29:52: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] for (i=1;i<=m;++i) {scanf("%d%d%d", &x, &y, &c); a[x].push_back(make_pair(c, y));} ^