Compilare: user.cpp: In function ‘void add(std::vector<int>&, std::vector<int>)’: user.cpp:30:40: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = a.size() ; i < b.size() ; ++i) ^ user.cpp:33:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0 ; i < a.size() || i < b.size() ; ++i) ^ user.cpp:33:49: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0 ; i < a.size() || i < b.size() ; ++i) ^ user.cpp:35:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (i < b.size()) a[i] += b[i]; ^ user.cpp: In function ‘int main()’: user.cpp:47:34: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("indep.in" , "r" , stdin); ^ user.cpp:48:36: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("indep.out" , "w" , stdout); ^ user.cpp:50:17: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d" , &N); ^ user.cpp:55:24: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d" , &x[i]); ^