vpll convex_hull (vpll points) {
i64 xmin = points[0].x_;
int min = 0;
for (int i = 1; i < points.size(); ++i) {
if ((points[i].x_ < xmin) || (xmin == points[i].x_ && points[i].y_ < points[min].y_)) {
xmin = points[i].x_;
min = i;
}
}
//cout << "min" << points[min].x_ << ' ' << points[min].y_ << endl;
swap(points[0], points[min]);
p0 = points[0];
sort(points.begin() + 1, points.end(), &cmp);
for (int i = 0; i < points.size(); ++i) {
cout << points[i].x_ << " " << points[i].y_ << endl;
}
/*
for (int i = 0; i < points.size(); ++i) {
cout << points[i].x_ << " " << points[i].y_ << endl;
}
*/
vpll stack;
stack.pb(points[0]);
stack.pb(points[1]);
stack.pb(points[2]);
for (int i = 3; i < points.size(); ++i) {
int n = stack.size();
//cout << "stack_size: " << n << endl;
while (orientation(stack[n - 2], stack[n - 1], points[i])) {
//cout << "pop\n";
stack.pop_back();
n = stack.size();
}
//cout << "push: " << points[i].x_ << ' ' << points[i].y_ << endl;
stack.pb(points[i]);
}
return stack;
}
