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  1. #include <algorithm>
  2. #include <chrono>
  3. #include <iostream>
  4. #include <iterator>
  5. #include <list>
  6. #include <map>
  7. #include <string>
  8. #include <utility>
  9. #include <numeric>
  10. #include <vector>
  11.  
  12.  
  13. template<typename T, typename K>
  14. std::vector<K> sum_elements(const T& beg, const T& end, std::size_t k, K def)
  15. {
  16.  if (k == 0) {
  17.      return std::vector<K>{};
  18.  }
  19.  return sum_elements(beg, end, k, def, [](auto &l, auto &r){ return r+l;});
  20. }
  21.  
  22. template<typename T, typename K, class BinaryOp>
  23. std::vector<K>
  24.     sum_elements(
  25.             const T& beg,
  26.             const T& end,
  27.             std::size_t k,
  28.             K def,
  29.             BinaryOp op)
  30. {
  31.     std::vector<K> out;
  32.     out.reserve((std::distance(beg, end) - 1)/k + 1);
  33.     for (auto it = beg; it!=end; std::advance(it, std::min(static_cast<std::size_t>(std::distance(it, end)), k)))
  34.     {
  35.         out.push_back(std::accumulate(it, std::next(it, std::min(static_cast<std::size_t>(std::distance(it, end)), k)), def, op));
  36.     }
  37.     return out;
  38. }
  39.  
  40. int main()
  41. {
  42.     std::vector<int> vec;
  43.     auto size = 1000000;
  44.     vec.reserve(size);
  45.     for (int i=0; i < size; ++i)
  46.         vec.push_back(i);
  47.     auto beg = std::chrono::system_clock::now();
  48.     auto sum = 0;
  49.     for (int i=0; i < 100; i++)
  50.         sum += sum_elements(vec.begin(), vec.end(), 2, 0).size();
  51.     auto end = std::chrono::system_clock::now();
  52.     std::cout << std::chrono::duration_cast<std::chrono::microseconds>(end-beg).count() << std::endl;
  53.     std::cout << sum << std::endl;
  54.  
  55.     return sum;
  56. }
  57.  
Runtime error #stdin #stdout 0.11s 17328KB
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stdin
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Standard input is empty
stdout
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112809
50000000
https://ideone.com/X1pyXG
language:
C++14 (gcc 8.3)
created:
6 years ago
visibility:
public

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