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  1. #include <iostream>
  2. #include <cmath>
  3. using namespace std;
  4.  
  5. double f(double x) {
  6.     return 2 * x * x * x + 3 * x - 1;
  7. }
  8.  
  9. int main() {
  10.     double x1 = 0, x2 = 1, x0, f1, f2, f0;
  11.     double E = 1e-8;
  12.     int i = 0;
  13.  
  14.     f1 = f(x1);
  15.     f2 = f(x2);
  16.  
  17.     if (f1 * f2 > 0) {
  18.         cout << "No root in this interval.\n";
  19.         return 0;
  20.     }
  21.  
  22.     cout << "Iter\t x1\t\t x2\t\t x0\t\t f(x0)\n";
  23.  
  24.     while (fabs((x2 - x1) / x2) > E) {
  25.         i++;
  26.         x0 = (x1 + x2) / 2;
  27.         f0 = f(x0);
  28.  
  29.         cout << i << "\t" << x1 << "\t" << x2 << "\t" << x0 << "\t" << f0 << endl;
  30.  
  31.         if (f1 * f0 < 0)
  32.             x2 = x0;
  33.         else {
  34.             x1 = x0;
  35.             f1 = f0;
  36.         }
  37.     }
  38.  
  39.     cout << "\nApproximate root = " << (x1 + x2) / 2 << endl;
  40.     cout << "Total iterations = " << i << endl;
  41.  
  42.     return 0;
  43. }
  44.  
Success #stdin #stdout 0s 5316KB
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stdin
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4 
-2
stdout
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Iter	 x1		 x2		 x0		 f(x0)
1	0	1	0.5	0.75
2	0	0.5	0.25	-0.21875
3	0.25	0.5	0.375	0.230469
4	0.25	0.375	0.3125	-0.00146484
5	0.3125	0.375	0.34375	0.112488
6	0.3125	0.34375	0.328125	0.0550308
7	0.3125	0.328125	0.320312	0.0266657
8	0.3125	0.320312	0.316406	0.0125715
9	0.3125	0.316406	0.314453	0.00554611
10	0.3125	0.314453	0.313477	0.00203884
11	0.3125	0.313477	0.312988	0.00028655
12	0.3125	0.312988	0.312744	-0.000589259
13	0.312744	0.312988	0.312866	-0.000151383
14	0.312866	0.312988	0.312927	6.75765e-05
15	0.312866	0.312927	0.312897	-4.19049e-05
16	0.312897	0.312927	0.312912	1.28354e-05
17	0.312897	0.312912	0.312904	-1.45349e-05
18	0.312904	0.312912	0.312908	-8.4977e-07
19	0.312908	0.312912	0.31291	5.99279e-06
20	0.312908	0.31291	0.312909	2.57151e-06
21	0.312908	0.312909	0.312909	8.60869e-07
22	0.312908	0.312909	0.312908	5.54898e-09
23	0.312908	0.312908	0.312908	-4.22111e-07
24	0.312908	0.312908	0.312908	-2.08281e-07
25	0.312908	0.312908	0.312908	-1.01366e-07
26	0.312908	0.312908	0.312908	-4.79085e-08
27	0.312908	0.312908	0.312908	-2.11798e-08
28	0.312908	0.312908	0.312908	-7.81538e-09
29	0.312908	0.312908	0.312908	-1.1332e-09

Approximate root = 0.312908
Total iterations = 29
https://ideone.com/VG0JUq
language:
C++ (gcc 8.3)
created:
16 days ago
visibility:
public

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