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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.  
  8.     while (b - a > eps) {
  9.         // (1) find middle point
  10.         c = (a + b) / 2;
  11.  
  12.         // (2) calculate the function values
  13.         double fa = a * a * a - a - 2;
  14.         double fb = b * b * b - b - 2;
  15.         double fc = c * c * c - c - 2;
  16.  
  17.         // (3) determine which way to go
  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.     cout << "root ~ " << c << endl;
  27.     cout << "error ~ " << c * c * c - c - 2 << endl;
  28.  
  29.     return 0;
  30. }
Success #stdin #stdout 0s 5288KB
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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
https://ideone.com/rlhDL1
language:
C++ (gcc 8.3)
created:
131 days ago
visibility:
public

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