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  1. #include <iostream>
  2. #include <unordered_map>
  3. #include <functional>
  4. #include <vector>
  5. #include <iterator>
  6.  
  7. class Base
  8. {
  9.     public:
  10.     static Base* build(std::istream& in)
  11.     {
  12.         int x;
  13.         in >> x;
  14.         return new Base(x);
  15.     }
  16.     Base(int x) {};
  17.     virtual void whoAmI()
  18.     {
  19.         std::cout << "Base\n";
  20.     }
  21. };
  22.  
  23. class Derived: public Base
  24. {
  25.     public:
  26.     static Derived* build(std::istream& in)
  27.     {
  28.         int x, y;
  29.         in >> x >> y;
  30.         return new Derived(x, y);
  31.     }
  32.     Derived(int x, int y) : Base(x) {};
  33.     virtual void whoAmI() override
  34.     {
  35.         std::cout << "Derived\n";
  36.     }
  37. };
  38.  
  39. template <class OutputIterator>
  40. OutputIterator loadData(std::istream& in, OutputIterator it)
  41. {
  42.     using map_type = const std::unordered_map<int, std::function<Base*(std::istream&)>>;
  43.     static map_type builders = { {1, Base::build}, {2, Derived::build}, };
  44.     int x;
  45.     while(in >> x)
  46.         *it++ = builders.at(x)(in);
  47.     return it;
  48. }
  49.  
  50.  
  51. int main()
  52. {
  53.     std::vector<Base*> pointers;
  54.     loadData(std::cin, std::back_inserter(pointers));
  55.     for(auto p: pointers)
  56.         p -> whoAmI();
  57. }
  58.  
Success #stdin #stdout 0s 3480KB
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stdin
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1 9000 
2 42 14 
1 1 
1 64
2 2 2
2 33 444
x
stdout
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Base
Derived
Base
Base
Derived
Derived
https://ideone.com/9NBQln
language:
C++14 (gcc 8.3)
created:
9 years ago
visibility:
public

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