private int getRightLower(Hull left, Hull right, int leftIndex, int rightIndex) //O(n)
{
List <PointF> rightPoints = right.getPoints();
List <PointF> leftPoints = left.getPoints();
while (calculateSlope(leftPoints[leftIndex], rightPoints[right.getPrevIndex(rightIndex)]) <
calculateSlope(leftPoints[leftIndex], rightPoints[rightIndex]))
{
rightIndex = right.getPrevIndex(rightIndex);
}
return(rightIndex);
}
private int getLeftLower(Hull left, Hull right, int leftIndex, int rightIndex) //O(n)
{
List <PointF> leftPoints = left.getPoints();
List <PointF> rightPoints = right.getPoints();
while (calculateSlope(rightPoints[rightIndex], leftPoints[left.getNextIndex(leftIndex)]) >
calculateSlope(rightPoints[rightIndex], leftPoints[leftIndex]))
{
leftIndex = left.getNextIndex(leftIndex);
}
return(leftIndex);
}
public void Solve(List <System.Drawing.PointF> pointList)
{
// TODO: Insert your code here
//order points by x value
pointList = pointList.OrderBy(p => p.X).ToList(); //O(nlogn)
Hull solution = getHull(pointList, 0, "start");
Pen redPen = new Pen(Color.Red, 2.0f);
drawLines(solution.getPoints(), redPen);
Refresh();
}
private int getIndexForPoint(PointF point, Hull hull)
{
List <PointF> points = hull.getPoints();
for (int i = 0; i < points.Count; i++)
{
if (points[i].Equals(point))
{
return(i);
}
}
return(-100);
}
public Hull merge(Hull left, Hull right)
{
int rightMost = left.getRightMostIndex();
int leftMost = right.getLeftMostIndex();
int currentLeftIndex = rightMost;
int currentRightIndex = leftMost;
int upperLeft = -1;
int upperRight = -1;
int lowerLeft = -1;
int lowerRight = -1;
bool leftIndexChanged = false;
bool rightIndexChanged = false;
//iterate through at least once
bool firstRight = true;
bool firstLeft = true;
//get upper common tangent
while (leftIndexChanged || rightIndexChanged || firstLeft || firstRight)
{
if (firstRight || leftIndexChanged)
{
firstRight = false;
upperRight = getRightUpper(left, right, currentLeftIndex, currentRightIndex);
if (upperRight == currentRightIndex)
{
leftIndexChanged = false;
rightIndexChanged = false;
}
else
{
rightIndexChanged = true;
currentRightIndex = upperRight;
}
}
if (firstLeft || rightIndexChanged)
{
firstLeft = false;
upperLeft = getLeftUpper(left, right, currentLeftIndex, currentRightIndex);
if (upperLeft == currentLeftIndex)
{
leftIndexChanged = false;
rightIndexChanged = false;
}
else
{
leftIndexChanged = true;
currentLeftIndex = upperLeft;
}
}
}
//get lower common tangentt
currentLeftIndex = rightMost;
currentRightIndex = leftMost;
leftIndexChanged = false;
rightIndexChanged = false;
//iterate through at least once
firstRight = true;
firstLeft = true;
while (leftIndexChanged || rightIndexChanged || firstLeft || firstRight)
{
if (firstLeft || rightIndexChanged)
{
firstLeft = false;
lowerLeft = getLeftLower(left, right, currentLeftIndex, currentRightIndex);
if (lowerLeft == currentLeftIndex)
{
leftIndexChanged = false;
rightIndexChanged = false;
}
else
{
leftIndexChanged = true;
currentLeftIndex = lowerLeft;
}
}
if (firstRight || leftIndexChanged)
{
firstRight = false;
lowerRight = getRightLower(left, right, currentLeftIndex, currentRightIndex);
if (lowerRight == currentRightIndex)
{
leftIndexChanged = false;
rightIndexChanged = false;
}
else
{
rightIndexChanged = true;
currentRightIndex = lowerRight;
}
}
}
//join points
List <PointF> resultPoints = new List <PointF>();
//add up to (and including) upperLeft
for (int i = 0; i <= upperLeft; i++)
{
resultPoints.Add(left.getPoints()[i]);
}
//add up to lowerRight
for (int i = upperRight; i != lowerRight; i = right.getNextIndex(i))
{
resultPoints.Add(right.getPoints()[i]);
}
//add lowerRight
resultPoints.Add(right.getPoints()[lowerRight]);
//add from lowerLeft to beginning
for (int i = lowerLeft; i != 0; i = left.getNextIndex(i))
{
resultPoints.Add(left.getPoints()[i]);
}
return(new Hull(resultPoints));
}
