Compilare: user.cpp: In function ‘void dijkstra(int)’: user.cpp:22:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < adj[u].size(); i++) { ^ user.cpp: In function ‘void dijkstra2(int)’: user.cpp:44:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < adj[u].size(); i++) { ^ user.cpp: In function ‘int main()’: user.cpp:57:36: 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:58:38: 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:59:24: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d", &N, &M); ^ user.cpp:63:32: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d %d", &x, &y, &w); ^