//code
class CalcArea
{
//点
public class Point
{
private double x;
private double y;
public Point(double a, double b)
{
x = a;
y = b;
}
public double getX()
{
return x;
}
public double getY()
{
return y;
}
public void setX(double a)
{
x = a;
}
public void setY(double b)
{
y = b;
}
}
//边
public class Line
{
private Point p1;
private Point p2;
public Line(Point x, Point y)
{
p1 = x;
p2 = y;
}
public Point getP1()
{
return p1;
}
public Point getP2()
{
return p2;
}
public void setP1(Point x)
{
p1 = x;
}
public void setP2(Point x)
{
p2 = x;
}
}
//三角形
public class Triangle
{
private Point p1;
private Point p2;
private Point p3;
public Triangle(Point a, Point b, Point c)
{
p1 = a;
p2 = b;
p3 = c;
}
public Point getP1()
{
return p1;
}
public Point getP2()
{
return p2;
}
public Point getP3()
{
return p3;
}
public void setP1(Point x)
{
p1 = x;
}
public void setP2(Point x)
{
p2 = x;
}
public void setP3(Point x)
{
p3 = x;
}
}
//计算三角形面积
public class Util
{
//计算两点间距离
public static double dispp(Point p1, Point p2)
{
double distX = p1.getX() - p2.getX();
double distY = p1.getY() - p2.getY();
return Math.Sqrt(distX * distX + distY * distY);
}
//点到直线的距离
public static double displ(Point p, Line l)
{
double lx1 = l.getP1().getX();
double lx2 = l.getP2().getX();
double ly1 = l.getP1().getY();
double ly2 = l.getP2().getY();
double k = (ly2 - ly1) / (lx2 - lx1);
double b = ly1 - k * lx1;
return Math.Abs((p.getY() - k * p.getX() - b)) / Math.Sqrt((k * k + 1));
}
//计算面积
public static double triArea(Triangle t)
{
Line l = new Line(t.getP1(), t.getP2());
return Util.dispp(t.getP1(), t.getP2()) * Util.displ(t.getP3(), l) / 2;
}
//向量方法计算
public static double triArea1(Triangle t)
{
double area = 0;
double a = Util.dispp(t.getP1(), t.getP2());
double b = Util.dispp(t.getP2(), t.getP3());
double c = Util.dispp(t.getP1(), t.getP3());
double d = (a + b + c) / 2;
area = Math.Sqrt(d * (d - a) * (d - b) * (d - c));
return area;
}
}
}
//test code
#region testTriangle
/// <summary>
/// 计算点在不在三角形内部
/// </summary>
private void testTriangle()
{
CalcArea.Point p1 = new CalcArea.Point(-1, 1);
CalcArea.Point p2 = new CalcArea.Point(1, 0.5);
CalcArea.Point p3 = new CalcArea.Point(2, -3);
double x = 0.8;
double y = 0.3;
CalcArea.Point p4 = new CalcArea.Point(x, y);
CalcArea.Triangle t;
t = new CalcArea.Triangle(p1, p2, p3);
double sourceArea = Convert.ToDouble(CalcArea.Util.triArea(t));
t = new CalcArea.Triangle(p1, p2, p4);
double area1 = Convert.ToDouble(CalcArea.Util.triArea1(t));
t = new CalcArea.Triangle(p3, p2, p4);
double area2 = Convert.ToDouble(CalcArea.Util.triArea1(t));
t = new CalcArea.Triangle(p1, p3, p4);
double area3 = Convert.ToDouble(CalcArea.Util.triArea1(t));
if (sourceArea == (double)((int)((area1 + area2 + area3) * 100)) / 100)
{
Console.WriteLine("点在三角形内部！");
}
else
{
Console.WriteLine("点不在三角形内部！");
}
Console.ReadLine();
}
#endregion