private KDTreeNode CreateTreeNode(List <Point> pointList)
{
if (pointList.Count > 0)
{
// 计算方差
double xObtainVariance = ObtainVariance(CreateXList(pointList));
double yObtainVariance = ObtainVariance(CreateYList(pointList));
// 根据方差确定分裂维度
EnumDivisionType divisionType = SortListByXOrYVariances(xObtainVariance, yObtainVariance, ref pointList);
// 获得中位数
Point medianPoint = ObtainMedian(pointList);
int medianIndex = pointList.Count / 2;
// 构建节点
KDTreeNode treeNode = new KDTreeNode()
{
DivisionPoint = medianPoint,
DivisionType = divisionType,
LeftChild = CreateTreeNode(pointList.Take(medianIndex).ToList()),
RightChild = CreateTreeNode(pointList.Skip(medianIndex + 1).ToList())
};
return(treeNode);
}
else
{
return(null);
}
}
private Point BacktrcakSearch(Point searchPoint, Point nearestPoint)
{
if (backtrackStack.IsEmpty())
{
return(nearestPoint);
}
else
{
KDTreeNode trackNode = backtrackStack.Pop();
double backtrackDistance = ObtainDistanFromTwoPoint(searchPoint, trackNode.DivisionPoint);
double nearestPointDistance = ObtainDistanFromTwoPoint(searchPoint, nearestPoint);
if (backtrackDistance < nearestPointDistance)
{
KDTreeNode searchNode = new KDTreeNode()
{
DivisionPoint = trackNode.DivisionPoint,
DivisionType = trackNode.DivisionType,
LeftChild = trackNode.LeftChild,
RightChild = trackNode.RightChild
};
nearestPoint = DFSBackTrackingSearch(searchNode, searchPoint);
}
return(BacktrcakSearch(searchPoint, nearestPoint));
}
}
private Point DFSRightSearch(KDTreeNode node, Point searchPoint)
{
if (node.RightChild != null)
{
return(DFSSearch(node.RightChild, searchPoint));
}
else
{
return(node.DivisionPoint);
}
}
private Point DFSYsearch(KDTreeNode node, Point searchPoint)
{
if (node.DivisionPoint.Y > searchPoint.Y)
{
return(DFSLeftSearch(node, searchPoint));
}
else
{
return(DFSRightSearch(node, searchPoint));
}
}
private Point DFSBackTrackLeftSearch(KDTreeNode node, Point searchPoint)
{
if (node.LeftChild != null)
{
return(DFSSearch(node.LeftChild, searchPoint, false));
}
else
{
return(node.DivisionPoint);
}
}
private Point DFSBackTrackingSearch(KDTreeNode node, Point searchPoint)
{
backtrackStack.Push(node);
if (node.DivisionType == EnumDivisionType.X)
{
return(DFSBackTrackingXsearch(node, searchPoint));
}
else
{
return(DFSBackTrackingYsearch(node, searchPoint));
}
}
private Point DFSSearch(KDTreeNode node, Point searchPoint, bool pushStack = true)
{
if (pushStack == true)
{
backtrackStack.Push(node);
}
if (node.DivisionType == EnumDivisionType.X)
{
return(DFSXsearch(node, searchPoint));
}
else
{
return(DFSYsearch(node, searchPoint));
}
}
private Point DFSBackTrackingYsearch(KDTreeNode node, Point searchPoint)
{
if (node.DivisionPoint.Y > searchPoint.Y)
{
node.LeftChild = null;
Point rightSearchPoint = DFSBackTrackRightSearch(node, searchPoint);
node.RightChild = null;
return(rightSearchPoint);
}
else
{
node.RightChild = null;
Point leftSearchPoint = DFSBackTrackLeftSearch(node, searchPoint);
node.LeftChild = null;
return(leftSearchPoint);
}
}
public void CreateByPointList(List <Point> pointList)
{
rootNode = CreateTreeNode(pointList);
}