C#高效实现一元高次多项式实根求解器

    /// <summary>
    /// 求解单一未知数多项式方程，c0+c1*x^1+c2*x^2+c3*x^3+...+cn*x^n=0
    /// </summary>
    public class SingleUnknownPolynomialSolver
    {
        /// <summary>
        /// 传入系数数组，构建实例
        /// </summary>
        /// <param name="coefs">方程系数：c0、c1、c2、c3、...、cn</param>
        public SingleUnknownPolynomialSolver(params double[] coefs)
        {
            if (coefs == null) _c = null;
            int cLength = 0;
            for (int i = 0; i < coefs.Length; i++)
            {
                if (coefs[coefs.Length - 1 - i] == 0) continue;
                cLength = coefs.Length - i;
                break;
            }
            _c = coefs.Take(cLength).ToArray();
        }


        private double[] _c;
        private Mathematics.ApproxEqual _approx = new Mathematics.ApproxEqual();

        /// <summary>
        /// 获取或设置近似相等比较器，近似相等比较器不可以为null，如果设置null则使用默认的近似相等比较器
        /// </summary>

        public Mathematics.ApproxEqual ApproxEqual
        {
            get => _approx;
            set
            {
                if (value == null) _approx = new Mathematics.ApproxEqual();
                else _approx = value;
            }
        }

        /// <summary>
        /// 求解方程的所有实数解
        /// </summary>
        /// <returns>返回所有实数解，无解返回空数组，无穷解返回null</returns>
        public double[] Solve()
        {
            if (_c == null || _c.Length == 0) return null;
            if (_c.Length == 1) return new double[] { };
            if (_c.Length == 2) return new double[] { -_c[0] / _c[1] };
            if (_c.Length == 3)
            {
                double delta = _c[1] * _c[1] - 4 * _c[0] * _c[2];
                if (delta < 0) return new double[] { };
                double sqrtDelta = Math.Sqrt(delta);
                if (_approx.IsEqual(sqrtDelta / _c[2], 0)) return new double[] { -_c[1] / _c[2] / 2 };
                return new double[] { (-_c[1] + sqrtDelta) / _c[2] / 2, (-_c[1] - sqrtDelta) / _c[2] / 2 };
            }
            var partialSolver = PartialSolver();
            var partialSolutions = partialSolver.Solve();
            if (partialSolutions.Length == 0)