Compilare: user.cpp: In function ‘int main()’: user.cpp:20:38: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j = 0; j < v[i].size() ; ++j) ^ user.cpp:22:38: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j = 0; j < v[i].size() ; ++j) ^ user.cpp:9:38: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("invsort.in", "r", stdin); ^ user.cpp:10:40: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("invsort.out", "w", stdout); ^ user.cpp:11:20: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &n); ^ user.cpp:13:24: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &x); ^