C# 点在多边形内

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c# 测试代码

namespace _062001
{
    class Program
    {
        static void Main(string[] args)
        {
            Point[] data = new Point[4];
            data[0] = new Point(0, 0);
            data[1] = new Point(0, 5);
            data[2] = new Point(5, 5);
            data[3] = new Point(5, 0);

            Point p = new Point(3, 3);
            if (PIP(p,data,4))
            {
                Console.WriteLine("在区域内");
            }else{
                Console.WriteLine("不在区域内");
            }
        }

        static bool PIP(Point p,Point[] data,int n)
        {
            bool flag =false;
            for (int i=0;i<n;i++)
            {
                if (p.Y <data[i].Y && p.Y<data[(i+1)%n].Y)
                      continue;
                if (data[i].X <p.X && data[(i+1)%n].X <p.X)
                      continue;
                float dx = data[(i+1)%n].X - data[i].X;
                float dy = data[(i+1)%n].Y - data[i].Y;
                float t= (float)((p.X - data[i].X)/dx);
                float y = t*dx + data[i].Y;
                if (y<p.Y && t>=0 && t<=1)
                      flag =!flag;
            }
            return flag;
        }
    }
    class Point
    {
        private float x;

        public float X
        {
            get { return x; }
            set { x = value; }
        }
        private float y;
        public float Y
        {
            get { return y; }
            set { y = value; }
        }

        public Point(float p_x,float p_y)
        {
            x = p_x;
            y = p_y;
        }

    }
   
}