using System;
using System.Collections.Generic;namespace ConsoleApp2
{internal class Program{static void Main(string[] args){List<Tuple<double, double>> points = new List<Tuple<double, double>>();points.Add(Tuple.Create(0.0, 1.0));points.Add(Tuple.Create(1.0, 0.0));points.Add(Tuple.Create(2.0, 1.0));points.Add(Tuple.Create(1.0, 2.0));Operator2D.FitCircle(points,out double centerX,out double centerY, out double radius);}}}class Operator2D
{public static void FitCircle(List<Tuple<double, double>> points, out double centerX, out double centerY, out double radius){double[,] ATA = new double[3, 3];double[] ATB = new double[3];foreach (var pt in points){double x = pt.Item1, y = pt.Item2;double twoX = 2 * x, twoY = 2 * y;double B_i = x * x + y * y;// 構建ATA矩陣ATA[0, 0] += twoX * twoX;ATA[0, 1] += twoX * twoY;ATA[0, 2] += twoX;ATA[1, 0] += twoY * twoX;ATA[1, 1] += twoY * twoY;ATA[1, 2] += twoY;ATA[2, 0] += twoX;ATA[2, 1] += twoY;ATA[2, 2] += 1;// 構建ATB向量ATB[0] += twoX * B_i;ATB[1] += twoY * B_i;ATB[2] += B_i;}// 計算逆矩陣double[,] invATA = Invert3x3Matrix(ATA);// 求解參數double a = invATA[0, 0] * ATB[0] + invATA[0, 1] * ATB[1] + invATA[0, 2] * ATB[2];double b = invATA[1, 0] * ATB[0] + invATA[1, 1] * ATB[1] + invATA[1, 2] * ATB[2];double c = invATA[2, 0] * ATB[0] + invATA[2, 1] * ATB[1] + invATA[2, 2] * ATB[2];// 計算半徑double rSquared = a * a + b * b + c;if (rSquared < 0) throw new ArgumentException("無法擬合有效圓形");radius = Math.Sqrt(rSquared);centerX = a;centerY = b;}// 3x3矩陣求逆static double[,] Invert3x3Matrix(double[,] matrix){double a = matrix[0, 0], b = matrix[0, 1], c = matrix[0, 2];double d = matrix[1, 0], e = matrix[1, 1], f = matrix[1, 2];double g = matrix[2, 0], h = matrix[2, 1], i = matrix[2, 2];double det = a * (e * i - f * h) - b * (d * i - f * g) + c * (d * h - e * g);if (Math.Abs(det) < 1e-12) throw new ArgumentException("矩陣不可逆");double invDet = 1.0 / det;return new double[,]{{ (e * i - f * h) * invDet, (c * h - b * i) * invDet, (b * f - c * e) * invDet },{ (f * g - d * i) * invDet, (a * i - c * g) * invDet, (c * d - a * f) * invDet },{ (d * h - e * g) * invDet, (b * g - a * h) * invDet, (a * e - b * d) * invDet }};}
}