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  1. #include <algorithm>
  2. #include <iostream>
  3. #include <iterator>
  4. #include <tuple>
  5. #include <vector>
  6.  
  7. template<typename T>
  8. struct in_situ_pair
  9. : std::iterator<std::forward_iterator_tag, std::pair<T, T>> {
  10.  
  11. 	using pair = std::pair<T, T>;
  12.  
  13. 	in_situ_pair(std::vector<T>& cont, std::size_t idx)
  14. 	: cont_(cont), index_{ idx }
  15. 	{ }
  16.  
  17. 	pair operator*() const {
  18. 		return { cont_[index_], cont_[(index_ + 1) % cont_.size()] };
  19. 	}
  20.  
  21. 	in_situ_pair& operator++() {
  22. 		++index_;
  23. 		return *this;
  24. 	}
  25.  
  26. 	bool operator==(const pair& r) const {
  27. 		const pair l = operator*();
  28. 		return 	(l.first == r.first && l.second == r.second)
  29. 				|| (l.first == r.second && l.second == r.first);
  30. 	}
  31.  
  32. 	bool operator==(const in_situ_pair& o) const {
  33. 		return (index_ == o.index_);
  34. 	}
  35.  
  36. 	bool operator!=(const in_situ_pair& o) const {
  37. 		return !(*this == o);
  38. 	}
  39. public:
  40. 	friend bool operator==(const pair& l, const in_situ_pair& r) {
  41. 		return (r == l);
  42. 	}
  43. private:
  44. 	std::vector<T>& cont_;
  45. 	std::size_t index_;
  46. };
  47.  
  48. template<typename T>
  49. using pair_of = std::pair<T, T>;
  50.  
  51. template<typename T>
  52. std::ostream & operator <<(std::ostream & stream, const pair_of<T>& pair) {
  53. 	return stream << '[' << pair.first << ", " << pair.second << ']';
  54. }
  55.  
  56. namespace in_situ {
  57. 	template<typename T>
  58. 	in_situ_pair<T> begin(std::vector<T>& cont) { return { cont, 0 }; }
  59.  
  60. 	template<typename T>
  61. 	in_situ_pair<T> end(std::vector<T>& cont) { return { cont, cont.size() }; }
  62.  
  63. 	template<typename T>
  64. 	in_situ_pair<T> at(std::vector<T>& cont, std::size_t i) { return { cont, i }; }
  65. }
  66.  
  67. int main() {
  68. 	std::vector<int>
  69. 		v1 {0 ,1, 2, 3, 4, 5},
  70. 		v2 {4, 8, 6, 2, 1, 5, 0, 3};
  71.  
  72. 	for(std::size_t i = 0; i < v1.size(); ++i) {
  73. 		auto pos = std::find(in_situ::begin(v2), in_situ::end(v2), in_situ::at(v1, i));
  74. 		if(pos != in_situ::end(v2)) {
  75. 			std::cout << "common: " << *pos << std::endl;
  76. 		}
  77. 	}
  78. }
Success #stdin #stdout 0s 3472KB
comments ()
stdin 
Standard input is empty
stdout 
common: [2, 1]
common: [3, 4]
common: [5, 0]
https://ideone.com/7cPZ0v
language:
C++14 (gcc 8.3)
created:
11 years ago
visibility:
secret

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