Compilare: user.cpp: In function ‘int main()’: user.cpp:18:34: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("grafc.in","r",stdin); ^ user.cpp:19:36: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("grafc.out","w",stdout); ^ user.cpp:25:38: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d %d", &k, &n, &m); ^ user.cpp:49:72: warning: ‘j’ may be used uninitialized in this function [-Wmaybe-uninitialized] for(i=1;i<=ans_size;i++) printf("%d %d\n", ans1[i], ans2[j]); ^