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  1. #include <iostream>          //id=240242103
  2. #include <cmath> 
  3. #include <iomanip>
  4. using namespace std;
  5.  
  6. // Horner's rule to evaluate f(x)
  7. double horner(double coeff[], int n, double x) {
  8.     double result = coeff[n];
  9.     for (int i = n - 1; i >= 0; i--)
  10.         result = result * x + coeff[i];
  11.     return result;
  12. }
  13.  
  14. int main() {
  15.     int degree;
  16.     cout << "Enter the degree of the polynomial: ";
  17.     cin >> degree;
  18.  
  19.     double coeff[degree + 1];
  20.     for (int i = 0; i <= degree; i++) {
  21.         cout << "x^" << i << "::";
  22.         cin >> coeff[i];
  23.     }
  24.  
  25.     double x1, x2, tol;
  26.     cout << "Enter first initial guess x1: ";
  27.     cin >> x1;
  28.     cout << "Enter second initial guess x2: ";
  29.     cin >> x2;
  30.     cout << "Enter tolerance: ";
  31.     cin >> tol;
  32.  
  33.     double f1 = horner(coeff, degree, x1);
  34.     double f2 = horner(coeff, degree, x2);
  35.     double x3, f3;
  36.     int iter = 0;
  37.  
  38.     cout << fixed << setprecision(6);
  39.     cout << "Iteration  x1        x2        x3        f(x3)\n";
  40.     cout << "--------------------------------------------\n";
  41.  
  42.     do {
  43.         x3 = (f2 * x1 - f1 * x2) / (f2 - f1); // Secant formula
  44.         f3 = horner(coeff, degree, x3);
  45.  
  46.         iter++;
  47.         cout << iter << "\t" << x1 << "\t" << x2 << "\t" << x3 << "\t" << f3 << endl;
  48.  
  49.         // Update for next iteration
  50.         x1 = x2;
  51.         f1 = f2;
  52.         x2 = x3;
  53.         f2 = f3;
  54.  
  55.     } while (fabs(f3) > tol); // Stop when residual < tolerance
  56.  
  57.     cout << "--------------------------------------------\n";
  58.     cout << "Approximate root = " << x3 << endl;
  59.  
  60.     return 0;
  61. }
  62.  
Success #stdin #stdout 0.01s 5276KB
comments (?)
stdin
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3
-3
-1
0
1
4
2
0.000001
stdout
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Enter the degree of the polynomial: x^0::x^1::x^2::x^3::Enter first initial guess x1: Enter second initial guess x2: Enter tolerance: Iteration  x1        x2        x3        f(x3)
--------------------------------------------
1	4.000000	2.000000	1.888889	1.850480
2	2.000000	1.888889	1.710024	0.290396
3	1.888889	1.710024	1.676730	0.037265
4	1.710024	1.676730	1.671828	0.000947
5	1.676730	1.671828	1.671700	0.000003
6	1.671828	1.671700	1.671700	0.000000
--------------------------------------------
Approximate root = 1.671700
https://ideone.com/GV6cwC
language:
C++ (gcc 8.3)
created:
15 hours ago
visibility:
public

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