Compilare: user.cpp: In function ‘void dfs(int)’: user.cpp:38:8: warning: suggest explicit braces to avoid ambiguous ‘else’ [-Wparentheses] if (leaf) ^ user.cpp: In function ‘void add(int, int)’: user.cpp:44:32: warning: the address of ‘f’ will always evaluate as ‘true’ [-Waddress] if ((is_edge(node, to) && !f) || (!is_edge(node, to) && f)) ^ user.cpp:44:61: warning: the address of ‘f’ will always evaluate as ‘true’ [-Waddress] if ((is_edge(node, to) && !f) || (!is_edge(node, to) && f)) ^ user.cpp: In function ‘int main()’: user.cpp:64:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("biperm.in","r",stdin); ^ user.cpp:65:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("biperm.out","w",stdout); ^ user.cpp:67:20: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &n); ^ user.cpp:69:27: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &a[i]); ^ user.cpp:71:27: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &b[i]); ^