//求散点子集的凸包
private IPositionSet solveHelp(IPosition p1, IPosition p2, IPositionSet ps)
{
//求离p1，p2最远的点
ps.InitToTraverseSet();
if (!ps.NextPosition())
{
return(ps);
}
IPosition p3 = ps.GetPosition();
double p3_h = getH(p1, p2, p3);
PositionSetEdit_ImplementByICollectionTemplate rest = new PositionSetEdit_ImplementByICollectionTemplate();
while (ps.NextPosition())
{
IPosition pt = ps.GetPosition();
double pt_h = getH(p1, p2, pt);
if (pt_h > p3_h)
{
rest.AddPosition(p3);
p3 = pt;
p3_h = pt_h;
}
else
{
rest.AddPosition(pt);
}
}
//把散点分成几部分
PositionSetEdit_ImplementByICollectionTemplate leftpart = new PositionSetEdit_ImplementByICollectionTemplate();
PositionSetEdit_ImplementByICollectionTemplate rightpart = new PositionSetEdit_ImplementByICollectionTemplate();
PositionSetEdit_ImplementByICollectionTemplate p1set = new PositionSetEdit_ImplementByICollectionTemplate();
PositionSetEdit_ImplementByICollectionTemplate p2set = new PositionSetEdit_ImplementByICollectionTemplate();
ps = rest;
IPosition p11 = new Position_Point(2 * p2.GetX() - p1.GetX(), 2 * p2.GetY() - p1.GetY()); //p1关于p2的对称点
double leftangle = getAngle(p1, p2, p3);
double rightangle = getAngle(p2, p11, p3);
ps.InitToTraverseSet();
while (ps.NextPosition())
{
IPosition p = ps.GetPosition();
if (p.GetX() == p1.GetX() && p.GetY() == p1.GetY())
{
p1set.AddPosition(p);
}
else if (p.GetX() == p2.GetX() && p.GetY() == p2.GetY())
{
p2set.AddPosition(p);
}
else if (p.GetX() == p3.GetX() && p.GetY() == p3.GetY())
{
leftpart.AddPosition(p);
}
else
{
double a = getAngle(p1, p2, p);
if (a > leftangle)
{
leftpart.AddPosition(p);
}
a = getAngle(p2, p11, p);
if (a < rightangle)
{
rightpart.AddPosition(p);
}
}
}
//对子集求解
IPositionSet subResult1 = solveHelp(p1, p3, leftpart);
IPositionSet subResult2 = solveHelp(p3, p2, rightpart);
//合并各部分解
PositionSetEdit_ImplementByICollectionTemplate result = new PositionSetEdit_ImplementByICollectionTemplate();
p1set.InitToTraverseSet();
while (p1set.NextPosition())
{
result.AddPosition(p1set.GetPosition());
}
subResult1.InitToTraverseSet();
while (subResult1.NextPosition())
{
result.AddPosition(subResult1.GetPosition());
}
result.AddPosition(p3);
subResult2.InitToTraverseSet();
while (subResult2.NextPosition())
{
result.AddPosition(subResult2.GetPosition());
}
p2set.InitToTraverseSet();
while (p2set.NextPosition())
{
result.AddPosition(p2set.GetPosition());
}
return(result);
}