Compilare: user.c: In function ‘knapsack_On2_space’: user.c:39: warning: unused variable ‘j’ user.c: In function ‘main’: user.c:62: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result user.c:63: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result user.c:69: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result user.c:75: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result