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  1. #include <iostream>
  2.  
  3. template <unsigned N>
  4. class element {
  5. public:
  6.     const static unsigned value = N;
  7. };
  8.  
  9. template <typename ...Elems>
  10. class set{};
  11.  
  12. template <typename ...Elems>
  13. void print(set<Elems...> t) {
  14.     std::cout << "{";
  15.     t.print();
  16.     std::cout << "}";
  17. }
  18.  
  19. template <typename Elem, typename ...Elems>
  20. class set<Elem, Elems...> {
  21. public:
  22.     static void print()
  23.     {
  24.         ::print(Elem());
  25.         std::cout << ", ";
  26.         set<Elems...>::print();
  27.     }
  28. };
  29.  
  30. template <typename Elem>
  31. class set<Elem> {
  32. public:
  33.     static void print()
  34.     {
  35.         ::print(Elem());
  36.     }
  37. };
  38.  
  39. template <unsigned N, typename ...Elems>
  40. class set<element<N>, Elems...> {
  41. public:
  42.     static void print()
  43.     {
  44.         std::cout << N << ", ";
  45.         set<Elems...>::print();
  46.     }
  47. };
  48.  
  49. template <unsigned N>
  50. class set<element<N>> {
  51. public:
  52.     static void print()
  53.     {
  54.         std::cout << N;
  55.     }
  56. };
  57.  
  58. template <>
  59. class set<> {
  60. public:
  61.     static void print(){}
  62. };
  63.  
  64. template <typename T, typename U>
  65. class join;
  66.  
  67. template <typename ...Elems>
  68. class join<set<>, set<Elems...>> {
  69. public:
  70.     typedef set<Elems...> type;
  71. };
  72.  
  73. template <typename Elem1, typename ...Elems, typename ...Elems2>
  74. class join<set<Elem1, Elems...>, set<Elems2...>> {
  75. public:
  76.     typedef typename join<set<Elems...>, set<Elem1, Elems2...>>::type type;
  77. };
  78.  
  79.  
  80. template <typename T, typename U>
  81. class all_subsets_worker;
  82.  
  83. template <typename Rest>
  84. class all_subsets_worker<set<>, Rest>
  85. {
  86. public:
  87.     typedef set<Rest> type;
  88. };
  89.  
  90. template <typename Elem, typename Rest, typename ...Elems>
  91. class all_subsets_worker<set<Elem, Elems...>, Rest>
  92. {
  93. public:
  94.     typedef typename join<
  95.                 typename all_subsets_worker<set<Elems...>, Rest>::type,
  96.                 typename all_subsets_worker<set<Elems...>, typename join< set<Elem>, Rest>::type >::type
  97.             >::type type;
  98. };
  99.  
  100. template <typename T>
  101. class all_subsets;
  102.  
  103. template <typename Elem, typename ...Elems>
  104. class all_subsets<set<Elem, Elems...>> {
  105. public:
  106.     typedef typename all_subsets_worker<set<Elem, Elems...>, set<>>::type type;
  107. };
  108.  
  109.  
  110.  
  111. int main(int argc, const char * argv[])
  112. {
  113.     auto t = all_subsets<set<element<0>, element<1>, element<2>, element<3>>>::type();
  114.  
  115.     print(t);
  116.  
  117.     std::cout << "\n";
  118.     return 0;
  119. }
Success #stdin #stdout 0s 2888KB
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stdin
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Standard input is empty
stdout
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{{3, 2, 1}, {2, 1}, {1}, {3, 1}, {3}, {}, {2}, {3, 2}, {3, 2, 0}, {2, 0}, {0}, {3, 0}, {3, 1, 0}, {1, 0}, {2, 1, 0}, {3, 2, 1, 0}}
https://ideone.com/jR6nTR
language:
C++14 (gcc 8.3)
created:
11 years ago
visibility:
public

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