C# 对于点位置的判断

1.判断点是否在一群点内部

要判断一个点是否在一个由多个点围成的多边形内部（例如一圈点），可以使用射线法（Ray Casting Algorithm）来实现。以下是一个简单的 C# 实现示例

using System;

public class Point
{
    public double X { get; set; }
    public double Y { get; set; }

    public Point(double x, double y)
    {
        X = x;
        Y = y;
    }
}

public class Program
{
    public static bool IsPointInPolygon(Point testPoint, Point[] polygon)
    {
        bool inside = false;
        int count = polygon.Length;
        for (int i = 0, j = count - 1; i < count; j = i++)
        {
            if (((polygon[i].Y > testPoint.Y) != (polygon[j].Y > testPoint.Y)) &&
                (testPoint.X < (polygon[j].X - polygon[i].X) * (testPoint.Y - polygon[i].Y) / (polygon[j].Y - polygon[i].Y) + polygon[i].X))
            {
                inside = !inside;
            }
        }
        return inside;
    }

    public static void Main()
    {
        Point[] polygon = new Point[]
        {
            new Point(