//worst case O(nlogn)
public void Solve(List <System.Drawing.PointF> pointList)
{
//sort points
pointList = pointList.OrderByDescending(p => p.X).ToList();
//call the recursive convexHull function, retrieve final list
Hull finalHUll = convexHUll(pointList);
pointList = finalHUll.getList();
//prepare list and draw it
PointF[] pointArray = pointList.ToArray();
g.DrawPolygon(new Pen(Color.Red), pointArray);
}
//worst case O(n)
public Hull combine(Hull left, Hull right)
{
//extract lists from hulls
List <PointF> l = left.getList();
List <PointF> r = right.getList();
//set booleans, they come in handy
bool bothDone = false;
bool rightDone = false;
bool leftDone = false;
//those 4 ints abreviate topleftindex,toprightindex,bottomleftindex,and bottomrightindex
int tli = left.getRightIndex();
int tri = 0;
int bli = left.getRightIndex();
int bri = 0;
//find top edge, repeat this loop until no change in left or right index
while (!bothDone)
{
bothDone = true;
rightDone = false;
leftDone = false;
//move right index "up" until no advantage in slope change
while (!rightDone)
{
int newIndex;
if (tri == 0)
{
newIndex = r.Count() - 1;
}
else
{
newIndex = tri - 1;
}
if (slope(l[tli], r[tri]) > slope(l[tli], r[newIndex]))
{
tri = newIndex;
bothDone = false;
}
else
{
rightDone = true;
}
}
//move left index "up" until no advantage in slope change
while (!leftDone)
{
int newIndex;
if (tli == (l.Count() - 1))
{
newIndex = 0;
}
else
{
newIndex = tli + 1;
}
if (slope(l[tli], r[tri]) < slope(l[newIndex], r[tri]))
{
tli = newIndex;
bothDone = false;
}
else
{
leftDone = true;
}
}
}
bothDone = false;
//find bottom edge, repeat this loop until no change in left or right index
while (!bothDone)
{
bothDone = true;
rightDone = false;
leftDone = false;
//move right index "down" until no advantage in slope change
while (!rightDone)
{
if (bri == (r.Count() - 1))
{
rightDone = true;
}
else
{
if (slope(l[bli], r[bri]) < slope(l[bli], r[bri + 1]))
{
bri++;
bothDone = false;
}
else
{
rightDone = true;
}
}
}
//move left index "down" until no advantage in slope change
while (!leftDone)
{
if (bli == 0)
{
leftDone = true;
}
else
{
if (slope(l[bli], r[bri]) > slope(l[bli - 1], r[bri]))
{
bli--;
bothDone = false;
}
else
{
leftDone = true;
}
}
}
}
//pass in the indeces we found
return(getNewHull(bli, bri, tri, tli, right.getRightIndex(), l, r));
}
