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  1.  
  2. #ifdef NDEBUG
  3. #undef NDEBUG
  4. #endif
  5. #include <cassert>
  6. #include <chrono>
  7. #include <functional>
  8. #include <iostream>
  9. #include <vector>
  10.  
  11. typedef unsigned long long Integer;
  12.  
  13. struct Functor
  14. {
  15.    void operator()(Integer i, Integer &sum) const
  16.    {
  17.       sum += i;
  18.       if ( i > 0 )
  19.       {
  20.          this->operator()(i - 1, sum);
  21.       }
  22.    }
  23. };
  24.  
  25. void recurse(Integer i, Integer& sum)
  26. {
  27.    sum += i;
  28.    if ( i > 0 )
  29.    {
  30.       recurse(i - 1, sum);
  31.    }
  32. }
  33.  
  34. int main()
  35. {
  36.    const Integer n(1000ull * 1000ull);
  37.    const auto t_0(std::chrono::high_resolution_clock::now());
  38.    Integer sum(0);
  39.    recurse(n, sum);
  40.    const auto t_1(std::chrono::high_resolution_clock::now());
  41.    std::function<void(Integer, Integer&)> lambda_recurse([&lambda_recurse](Integer i, Integer& l_sum)
  42.    {
  43.       l_sum += i;
  44.       if ( i > 0 )
  45.       {
  46.          lambda_recurse(i - 1, l_sum);
  47.       }
  48.    });
  49.    Integer lambda_sum(0);
  50.    lambda_recurse(n, lambda_sum);
  51.    const auto t_2(std::chrono::high_resolution_clock::now());
  52.    Integer functor_sum(0);
  53.    Functor functor;
  54.    functor(n, functor_sum);
  55.    const auto t_3(std::chrono::high_resolution_clock::now());
  56.    assert ( sum == lambda_sum );
  57.    assert ( sum == functor_sum );
  58.    std::cout << std::chrono::duration_cast<std::chrono::nanoseconds>(t_1 - t_0).count() << "\n";
  59.    std::cout << std::chrono::duration_cast<std::chrono::nanoseconds>(t_2 - t_1).count() << "\n";
  60.    std::cout << std::chrono::duration_cast<std::chrono::nanoseconds>(t_3 - t_2).count() << "\n";
  61. }
Success #stdin #stdout 0.01s 2984KB
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https://ideone.com/6vxOqt
language:
C++14 (gcc 8.3)
created:
10 years ago
visibility:
public

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