Eroare de compilare: user.cpp: In function ‘std::vector<std::pair<int, int> > convex(std::vector<std::pair<int, int> >)’: user.cpp:20:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i = 2; i < pts.size(); ++ i) { ^ user.cpp: In function ‘int main()’: user.cpp:44:32: error: ‘sort’ was not declared in this scope sort(sus.begin(), sus.end()); ^ user.cpp:50:35: error: ‘reverse’ was not declared in this scope reverse(jos.begin(), jos.end()); ^ user.cpp:55:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i = 0; i < sus.size() - 1; ++ i) { ^ user.cpp:56:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(j < jos.size() && ccw(sus[i], sus[i + 1], jos[j]) <= 0) ^ user.cpp:61:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(j == jos.size()) { ^ user.cpp:67:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i = 0; i < jos.size() - 1; ++ i) ^ user.cpp:31:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("oypara.in", "r", stdin); ^ user.cpp:32:39: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("oypara.out", "w", stdout); ^ user.cpp:35:20: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &n); ^ user.cpp:38:38: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d%d", &x, &y1, &y2); ^