Convex convexIntersection(Convex v1, Convex v2) {
vector<Halfplane> h;
for (int i = 0; i < v1.size(); i++) {
h.push_back(Halfplane(v1[i], v1[(i+1) % v1.size()]));
}
for (int i = 0; i < v2.size(); i++) {
h.push_back(Halfplane(v2[i], v2[(i+1) % v2.size()]));
}
return halfplaneIntersection(h);
}
double area(Convex a) {
double sum = 0;
a.push_back(a[0]);
for (int i = 0; i < a.size() - 1; i++) {
sum += cross(a[i], a[i+1]);
}
return sum / 2.0;
}
Convex convex_hull(Convex a) {
Convex res(2 * a.size() + 5);
sort(a.begin(), a.end(), comp_less);
a.erase(unique(a.begin(), a.end()), a.end());
int m = 0;
for (int i = 0; i < a.size(); i++) {
while (m > 1 && sgn(cross(res[m-1]-res[m-2], a[i]-res[m-2])) <= 0) {
m--;
}
res[m++] = a[i];
}
int k = m;
for (int i = a.size() - 2; i >= 0; i--) {
while (m > k && sgn(cross(res[m-1]-res[m-2], a[i]-res[m-2])) <= 0) {
m--;
}
res[m++] = a[i];
}
res.resize(m);
if (a.size() > 1) {
res.resize(m-1);
}
return res;
}
int main(int argc, char const *argv[])
{
Convex v1, v2;
v1.push_back(Point(0,0));
v1.push_back(Point(1,1));
v1.push_back(Point(0,2));
v1.push_back(Point(-1,1));
v1.push_back(Point(-0.5,0));
v2.push_back(Point(1,0));
v2.push_back(Point(2,1));
v2.push_back(Point(1,2));
v2.push_back(Point(0,1));
v2.push_back(Point(0.5,0));
Convex v = convexIntersection(v1, v2);
for (int i = 0; i < v.size(); ++i)
{
cout << v[i] << endl;
}
return 0;
}
Convex convexIntersection(Convex v1, Convex v2)
{
vector<Halfplane> h, h1, h2;
for (int i = 0; i < v1.size(); ++i)
h1.push_back(Halfplane(v1[i], v1[(i+1)%v1.size()]));
for (int i = 0; i < v2.size(); ++i)
h2.push_back(Halfplane(v2[i], v2[(i+1)%v2.size()]));
int p1 = 0, p2 = 0;
while(p1 < h1.size() && p2 < h2.size())
{
int res = sgn(arg(h1[p1].second - h1[p1].first) - arg(h2[p2].second - h2[p2].first));
if (res < 0)
h.push_back(h1[p1++]);
else if (res > 0)
h.push_back(h2[p2++]);
else
if (sgn(cross(h1[p1].first - h2[p2].first, h2[p2].second - h2[p2].first)) < 0)
{
h.push_back(h1[p1++]);
p2++;
}
else
{
h.push_back(h2[p2++]);
p1++;
}
}
while(p1 < h1.size())
h.push_back(h1[p1++]);
while(p2 < h2.size())
h.push_back(h2[p2++]);
deque<Halfplane> q;
deque<Point> ans;
q.push_back(h[0]);
for (int i = 1; i < int(h.size()); ++i)
{
if (sgn(arg(h[i].second - h[i].first) - arg(h[i-1].second - h[i-1].first)) == 0)
continue;
while (ans.size() > 0 && !satisfy(ans.back(), h[i]))
{
ans.pop_back();
q.pop_back();
}
while (ans.size() > 0 && !satisfy(ans.front(), h[i]))
{
ans.pop_front();
q.pop_front();
}
ans.push_back(crosspoint(q.back(), h[i]));
q.push_back(h[i]);
}
while (ans.size() > 0 && !satisfy(ans.back(), q.front()))
{
ans.pop_back();
q.pop_back();
}
while (ans.size() > 0 && !satisfy(ans.front(), q.back()))
{
ans.pop_front();
q.pop_front();
}
ans.push_back(crosspoint(q.back(), q.front()));
return vector<Point>(ans.begin(), ans.end());
}
