Compilare: user.cpp: In function ‘std::vector<point> convex_hull(std::vector<point>&)’: user.cpp:27:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 2; i < A.size(); i++) { ^ user.cpp: In function ‘int main()’: user.cpp:70:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i = 0; i < V.size(); i++) { ^ user.cpp:40:44: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("infasuratoare.in", "r", stdin); ^ user.cpp:41:46: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("infasuratoare.out", "w", stdout); ^ user.cpp:57:17: warning: ‘o_i’ may be used uninitialized in this function [-Wmaybe-uninitialized] A[0] = A[o_i]; ^