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Accepted
Philippe
Asked:2020-06-30 00:38:58 +0000 UTC2020-06-30 00:38:58 +0000 UTC

求多项式系数C#

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我正在编写一个能够使用此库求解方程/系统的程序。

我需要一种方法来轻松计算多项式的系数，例如：

string input = "(x - 5)(x + 2) = 0"
int degree = DeterminePolynomialDegree(input) //тут degree == 2
c#

1 个回答

  1. Best Answer

    我是这样得到的：

    using MathNet.Symbolics;
using Expr = MathNet.Symbolics.Expression;

    var expr = Infix.ParseOrThrow("(x - 5)*(x + 2)"); // без звёздочки не парсит :(
var expanded = Algebraic.Expand(expr);
var xsym = Expr.Symbol("x");
if (SingleVariablePolynomial.IsPolynomial(xsym, expanded))
{
    var degreeExpr = SingleVariablePolynomial.Degree(xsym, expanded);
    var degree = Evaluate.Evaluate(null, degreeExpr).RealValue;
    Console.WriteLine($"Degree: {degree}");
}
else
{
    Console.WriteLine("Not a polynomial in x");
}

    有了两个变量，就不再困难了：

    var expr = Infix.ParseOrThrow("(x - 5)*(x + 2) + x * y");
var expanded = Algebraic.Expand(expr);
var xsym = Expr.Symbol("x");
var ysym = Expr.Symbol("y");
var syms = new HashSet<Expr>() {xsym, ysym};
if (Polynomial.IsMultivariatePolynomial(syms, expanded))
{
    var degreeXExpr = Polynomial.Degree(xsym, expanded);
    var degreeX = Evaluate.Evaluate(null, degreeXExpr).RealValue;
    var degreeYExpr = Polynomial.Degree(ysym, expanded);
    var degreeY = Evaluate.Evaluate(null, degreeYExpr).RealValue;
    Console.WriteLine($"Degree X: {degreeX}, Y: {degreeY}");
}
else
{
    Console.WriteLine("Not a polynomial in (x, y)");
}
    • 3

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