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  1. #include <iostream>
  2. using namespace std;
  3.  
  4. int main() {
  5.  
  6. 	double a = 1, b = 2, c, eps = 1e-9;
  7. 	int cnt = 0;
  8.  
  9. 	while (b - a > eps) {
  10.  
  11. 		cnt++;
  12. 		c = (a + b) / 2;
  13.  
  14. 		double fa = a * a * a - a - 2;
  15. 		double fc = c * c * c - c - 2;
  16. 		double fb = b * b * b - b - 2;
  17.  
  18. 		// if ((fa > 0 && fc < 0) || (fa < 0 && fc > 0))
  19. 		if (fa * fc < 0) {
  20. 			b = c;
  21. 		} else {
  22. 			a = c;
  23. 		}
  24.  
  25. 	}
  26.  
  27. 	cout << "root ~ " << c << endl;
  28. 	double error = c * c * c - c - 2;
  29. 	cout << "error = " << error << endl;
  30. 	cout << "iterations = " << cnt << endl;
  31.  
  32. 	return 0;
  33.  
  34. }
Success #stdin #stdout 0s 4520KB
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stdin
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Standard input is empty
stdout
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root ~ 1.52138
error = -2.10862e-09
iterations = 30
https://ideone.com/QDEf4W
猜數字之二元搜尋
language:
C++14 (gcc 8.3)
created:
5 years ago
visibility:
secret

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