Compilare: user.cpp: In function ‘int main()’: user.cpp:20:34: warning: format ‘%lf’ expects argument of type ‘double*’, but argument 2 has type ‘long double*’ [-Wformat=] scanf("%lf", &a[i][j]); ^ user.cpp:48:49: warning: format ‘%lf’ expects argument of type ‘double’, but argument 2 has type ‘long double’ [-Wformat=] for(i=1; i<=n; ++i) printf("%.10lf ", ans[i]); ^ user.cpp:13:36: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("gauss.in", "r", stdin); ^ user.cpp:14:38: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("gauss.out", "w", stdout); ^ user.cpp:16:26: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d", &m, &n); ^ user.cpp:20:35: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%lf", &a[i][j]); ^