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  1. #include <iostream>
  2. #include <ctime>
  3. using namespace std;
  4.  
  5.     constexpr pair<double, double> helper(size_t n, const pair<double, double>& g)
  6.     {
  7.         return n % 2
  8.             ? make_pair(g.second * g.second + g.first * g.first, g.second * g.second + 2 * g.first * g.second)
  9.             : make_pair(2 * g.first * g.second - g.first * g.first, g.second * g.second + g.first * g.first);
  10.     }
  11.  
  12.     constexpr pair<double, double> fibonacciRecursive(size_t n)
  13.     {
  14.         return n < 2
  15.             ? make_pair<double, double>(n, 1)
  16.             : helper(n, fibonacciRecursive(n / 2));
  17.     }
  18.  
  19.     constexpr double fibonacci(size_t n)
  20.     {
  21.         return fibonacciRecursive(n).first;
  22.     }
  23.  
  24.  
  25. int main() {
  26. 	cout << "start\t " <<  time(NULL) << endl;
  27. 	cout << fibonacci(0) << endl;
  28. 	cout << fibonacci(1) << endl;
  29. 	cout << fibonacci(2) << endl;
  30. 	cout << fibonacci(3) << endl;
  31. 	cout << fibonacci(4) << endl;
  32. 	cout << fibonacci(5) << endl;
  33. 	cout << fibonacci(100) << endl;
  34. 	cout << "finish\t " << time(NULL) << endl;
  35. 	return 0;
  36. }
Success #stdin #stdout 0s 3296KB
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Standard input is empty
stdout
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start	 1396108588
0
1
1
2
3
5
3.54225e+20
finish	 1396108588
https://ideone.com/eXKd0t
language:
C++14 (gcc 8.3)
created:
10 years ago
visibility:
public

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