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  1. #include <iostream>
  2. #include <list>
  3. #include <numeric>
  4. #include <chrono>
  5. #include <string>
  6. #include <memory>
  7.  
  8. using namespace std;
  9.  
  10. template< typename T, template<typename, typename> class Container>
  11. class ContainerTemplate: public Container<T, allocator<T>>
  12. {
  13. public:
  14.     size_t inlet_whole_length()
  15.     {
  16.         size_t result(0);
  17.         for(auto it: *this)
  18.         {
  19.             result+=it.size();
  20.         }
  21.         return result;
  22.     }
  23.  
  24.  
  25.     T  whole_inlet_containers2container()
  26.     {
  27.         T result;
  28.         result.reserve(inlet_whole_length());
  29.         for(auto a:*this)result.insert(result.end(), a.begin(), a.end());
  30.         return result;
  31.     }
  32.  
  33. };
  34.  
  35. template< typename T, template<typename, typename> class Container>
  36. class ContainerTemplate2: public Container<T, allocator<T>>
  37. {
  38. public:
  39.     size_t inlet_whole_length()
  40.     {
  41.         size_t result(0);
  42.         for(const auto &it: *this) //ссылка важна здесь
  43.         {
  44.             result+=it.size();
  45.         }
  46.         return result;
  47.     }
  48.  
  49.  
  50.     T  whole_inlet_containers2container()
  51.     {
  52.         T result;
  53.         result.reserve(inlet_whole_length());
  54.         for(const auto &a:*this)result.insert(result.end(), a.begin(), a.end());
  55.         return result;
  56.     }
  57.  
  58. };
  59.  
  60. int main()
  61. {
  62.  
  63.     const std::size_t Size = 75000;
  64.     ContainerTemplate<string, list> vs;
  65.     ContainerTemplate2<string, list> vs2;
  66.  
  67.     for (std::size_t i = 0; i < Size; i++)
  68.     {
  69.         auto str = std::string(i,'s');
  70.         vs.push_back(str);
  71.         vs2.push_back(str);
  72.     }
  73.     auto start = std::chrono::high_resolution_clock::now();
  74.     auto str = vs.whole_inlet_containers2container();
  75.     auto end = std::chrono::high_resolution_clock::now();
  76.  
  77.     std::chrono::duration<double> diff = end-start;
  78.     std::cout << "Time without ref "<< diff.count() << " s\n";
  79.  
  80.     start = std::chrono::high_resolution_clock::now();
  81.     auto str2 = vs2.whole_inlet_containers2container();
  82.     end = std::chrono::high_resolution_clock::now();
  83.     diff = end-start;
  84.     std::cout << "Time with ref "<< diff.count() << " s\n";
  85. }
  86.  
Success #stdin #stdout 3.72s 320832KB
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stdin
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Standard input is empty
stdout
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Time without ref 1.29938 s
Time with ref 0.806544 s
https://ideone.com/ej4mM5
language:
C++14 (gcc 8.3)
created:
6 years ago
visibility:
public

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