Compilare: user.cpp: In function ‘void dfs(int)’: user.cpp:27:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0; i<a[nod].sons.size(); i++) ^ user.cpp: In function ‘int main()’: user.cpp:57:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("petsoft.in", "r", stdin); ^ user.cpp:58:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("petsoft.out", "w", stdout); ^ user.cpp:60:17: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &n); ^ user.cpp:64:18: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &x); ^