Compilare: user.cpp: In function ‘void write()’: user.cpp:59:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 1; i < len.size(); ++i) { ^ user.cpp: In function ‘int main()’: user.cpp:67:39: 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:68:41: 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); ^