public void Solve(System.Drawing.Graphics g, List <System.Drawing.PointF> pointList)
{
// Insert your code here.
//Add all the points to a SortedList sorted by x-value
// List<PointF> slist = new List<PointF>();
// for (int i = 0; i < pointList.Count; i++)
// {
// if (!slist.Contains(pointList[i]))
// {
// slist.Add(pointList[i]);
// }
// }
System.Collections.Generic.
HashSet <PointF> hashPoints = new HashSet <PointF>();
for (int i = 0; i < pointList.Count; i++)
{
hashPoints.Add(pointList[i]);
}
List <PointF> slist = ((IEnumerable <PointF>)hashPoints).ToList <PointF>();
slist.Sort(new XComparer());
//testing sorting visually
// drawList(g, slist);
//Start timer
// timeUp = DateTime.Now.AddSeconds(5);
//Recursively divide and conqueror
LList hull = divAndCon(g, slist);
drawLList(g, hull, new Pen(Color.Blue));
}
private void drawLList(Graphics g, LList hull, Pen pen)
{
//Font font = new Font("Arial", 10);
//Brush brush = new SolidBrush(Color.SteelBlue);
//g.DrawString("" + hull.Count, font, brush, new PointF(0F, 0F));
LLNode temp = hull.LeftMost;
if (hull.Count > 1)
{
do
{
//g.DrawEllipse(pen, temp.Point.X, temp.Point.Y, 5, 5);
g.DrawLine(pen, temp.Point, temp.Next.Point);
temp = temp.Next;
}while (temp.Point != hull.LeftMost.Point);
}
}
private LList divAndCon(Graphics g, List <PointF> slist)
{
if (slist.Count > 1)
{
//Find middle
int mid = slist.Count / 2;
float midX = slist[mid].X;
PointF minY = slist[0];
PointF maxY = slist[0];
//Separate into left and right lists
List <PointF> leftList = new List <PointF>();
List <PointF> rightList = new List <PointF>();
for (int i = 0; i < slist.Count; i++)
{
if (slist[i].X <= midX)
{
leftList.Add(slist[i]);
if (slist[i].Y < minY.Y)
{
minY = slist[i];
}
if (slist[i].Y > maxY.Y)
{
maxY = slist[i];
}
}
else
{
rightList.Add(slist[i]);
}
}
//if all points were added to the left list
if (rightList.Count <= 0)
{
LList skipper = new LList();
skipper.LeftMost = new LLNode(minY);
skipper.RightMost = new LLNode(maxY);
skipper.LeftMost.Next = skipper.RightMost;
skipper.LeftMost.Prev = skipper.RightMost;
skipper.RightMost.Next = skipper.LeftMost;
skipper.RightMost.Prev = skipper.LeftMost;
if (skipper.LeftMost.Point == skipper.RightMost.Point)
{
skipper.Count = 1;
}
else
{
skipper.Count = 2;
}
return(skipper);
}
LList leftLL = divAndCon(g, leftList);
LList rightLL = divAndCon(g, rightList);
return(combine(g, leftLL, rightLL));
}
else
{
LList llist = new LList();
LLNode one = new LLNode(slist[0]);
one.Next = one;
one.Prev = one;
llist.LeftMost = one;
llist.RightMost = one;
llist.Count = 1;
return(llist);
}
}
private LList combine(Graphics g, LList leftLL, LList rightLL)
{
//place holders for solution points
//(to manipulate next/prev pointers after completed testing)
LLNode left = leftLL.RightMost;
LLNode right = rightLL.LeftMost;
LLNode topLSol = left;
LLNode topRSol = right;
LLNode botLSol = left;
LLNode botRSol = right;
//Test top
Boolean found = false;
Boolean acceptRight;
Boolean acceptLeft;
while (!found)
{
acceptRight = false;
acceptLeft = false;
double m = (left.dY - right.dY) / (left.dX - right.dX);
double b = (-m * left.dX) + left.dY;
acceptRight = true;
if (rightLL.Count > 1)
{
LLNode testRight = right.Next;
if (m * testRight.dX + b - testRight.dY < 0)
{
right = testRight;
acceptRight = false;
}
else
{
if (rightLL.Count > 2)
{
testRight = right.Prev;
if (m * testRight.dX + b - testRight.dY < 0)
{
right = testRight;
acceptRight = false;
}
}
}
}
if (acceptRight)
{
acceptLeft = true;
if (leftLL.Count > 1)
{
LLNode testLeft = left.Prev;
if (m * testLeft.dX + b - testLeft.dY < 0)
{
left = testLeft;
acceptLeft = false;
}
else
{
if (leftLL.Count > 2)
{
testLeft = left.Next;
if (m * testLeft.dX + b - testLeft.dY < 0)
{
left = testLeft;
acceptLeft = false;
}
}
}
}
if (acceptLeft)
{
topLSol = left;
topRSol = right;
found = true;
}
}
}
//Test bottom
found = false;
left = leftLL.RightMost;
right = rightLL.LeftMost;
while (!found)
{
acceptRight = false;
acceptLeft = false;
double m = (left.dY - right.dY) / (left.dX - right.dX);
double b = (-m * left.dX) + left.dY;
acceptRight = true;
if (rightLL.Count > 1)
{
LLNode testRight = right.Prev;
if (m * testRight.dX + b - testRight.dY > 0)
{
right = testRight;
acceptRight = false;
}
else
{
if (rightLL.Count > 2)
{
testRight = right.Next;
if (m * testRight.dX + b - testRight.dY > 0)
{
right = testRight;
acceptRight = false;
}
}
}
}
if (acceptRight)
{
acceptLeft = true;
if (leftLL.Count > 1)
{
LLNode testLeft = left.Next;
if (m * testLeft.dX + b - testLeft.dY > 0)
{
left = testLeft;
acceptLeft = false;
}
else
{
if (leftLL.Count > 2)
{
testLeft = left.Prev;
if (m * testLeft.dX + b - testLeft.dY > 0)
{
left = testLeft;
acceptLeft = false;
}
}
}
}
if (acceptLeft)
{
botLSol = left;
botRSol = right;
found = true;
}
}
}
//Change pointers
topLSol.Prev = topRSol;
topRSol.Next = topLSol;
botLSol.Next = botRSol;
botRSol.Prev = botLSol;
//update leftmost and rightmost pointers in a new LList
LList nList = new LList();
nList.LeftMost = topLSol;
while (nList.LeftMost.Prev.dX < nList.LeftMost.dX)
{
nList.LeftMost = nList.LeftMost.Prev;
}
nList.RightMost = botRSol;
while (nList.RightMost.Next.dX > nList.RightMost.dX)
{
nList.RightMost = nList.RightMost.Next;
}
nList.UpdateCount();
return(nList);
}