Compilare: user.cpp: In function ‘int main()’: user.cpp:38:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<a[nxt].size();i++) ^ user.cpp:21:34: 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:22:36: 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); ^