Compilare: user.cpp: In function ‘int main()’: user.cpp:110:34: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen ("sortop.in", "r", stdin); ^ user.cpp:111:36: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen ("sortop.out", "w", stdout); ^ user.cpp:113:24: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf ("%d %d", &N, &K); ^ user.cpp:117:28: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf ("%d %d", &x, &y); ^ user.cpp:125:32: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf ("%d %d", &pos, &val); ^ user.cpp:132:54: warning: ‘X’ may be used uninitialized in this function [-Wmaybe-uninitialized] for (vector < int > :: iterator it = v[X].begin (); it != v[X].end (); it ++) ^