牛顿法解多项式的根

 给个初值，用牛顿法解多项式的根；

 

 

#include<iostream>
#include<math.h>
#include<vector>
using namespace std;

struct   Newton {
public:
 
    double ini_para;
   
    // 最高n次，系数列表，初值
    double resultNewton(int n,std::vector<double> coffer,double ini_para) {
        int c = 0;
      
        double x = ini_para, x2 = 0;
        while (true) {
            c++;
            double b;
            int i = 0;
            double yuanf = 0, daof = 0;
            while( i < n+1 ){
                 yuanf += coffer[i] * pow(x,n-i); // 原函数
                 if(i<n)
                     daof += (n-i)*coffer[i]*pow(x,n-i-1); //导函数
                 i++;
            }
            double chu = yuanf / daof; //原函数/导函数
            x2 = x - chu;
          
            if (abs(x2 - x) < 0.00001)
                break;
            x = x2;
        }
        int i = 0;
        double reslt = 0;
        while (i < n + 1) {
             reslt += coffer[i] * pow(x2, n - i); // 原函数 
            i++;
        }


        cout << "总共迭代了：" << c << "  "<< reslt;

        return x2;
    }
};


int main() {
   
    std::vector<double> coff = { 1,0 ,0,0,5,6};
    Newton newton;
    int a = newton.resultNewton(coff.size()-1, coff,-10);
    cout << "\n结果为：\n" << a << endl;
    system("pause");
    return 0;
}