Compilare: user.cpp: In function ‘void dfs(int)’: user.cpp:39:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i = 0; i < d[u].size(); i++) { ^ user.cpp: In function ‘int main()’: user.cpp:68:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i = 0; i < sol.size(); i++) { ^ user.cpp:69:36: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(j = 0; j < sol[i].size(); j++) ^ 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("biconex.in", "r", stdin); ^ user.cpp:59:40: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("biconex.out", "w", stdout); ^ user.cpp:60:27: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d", &N, &M); ^ user.cpp:62:31: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d", &x, &y); ^