Compilare: user.cpp: In function ‘void _mergesort(int, int)’: user.cpp:41:9: warning: unused variable ‘k’ [-Wunused-variable] k = 0, ^ user.cpp:43:9: warning: unused variable ‘i’ [-Wunused-variable] i, j; ^ user.cpp:43:12: warning: unused variable ‘j’ [-Wunused-variable] i, j; ^ user.cpp: In function ‘void read()’: user.cpp:13:30: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen(FIN, "r", stdin); ^ user.cpp:15:21: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &n); ^ user.cpp:19:49: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] for(i = 0; i < n; i++) scanf("%d", vec + i); ^ user.cpp: In function ‘void write()’: user.cpp:28:30: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen(FOUT, "w", stdout); ^