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  1. #include<iostream>
  2. #include<iomanip>
  3. #include<cmath>
  4. using namespace std;
  5. int n;
  6. double a[10];
  7. double f(double x)
  8. {
  9. 	double y=-1;
  10. 	for(int i=0;i<n;i++)
  11. 		y*=x-a[i];
  12. 	return y;
  13. }
  14. double solve(double l,double r)
  15. {
  16. 	while(r-l>=1e-7)
  17. 	{
  18. 		double lm=l+(r-l)/3;
  19. 		double rm=l+(r-l)/3*2;
  20. 		if(f(lm)>f(rm)){
  21. 			r=rm;
  22. 		}else{
  23. 			l=lm;
  24. 		}
  25. 	}
  26. 	return l;
  27. }
  28. int main()
  29. {
  30. 	cin>>n;
  31. 	for(int i=0;i<n;i++)
  32. 		cin>>a[i];
  33. 	int p;
  34. 	cin>>p;
  35. 	cout<<fixed<<setprecision(6)<<solve(a[p],a[p+1])<<endl;
  36. }
Success #stdin #stdout 0s 3432KB
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stdout
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54.000000
https://ideone.com/Tuut9E
language:
C++14 (gcc 8.3)
created:
9 years ago
visibility:
secret

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