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  1. #include <algorithm>
  2. #include <cstdio>
  3. #include <ctime>
  4. #include <iterator>
  5. #include <type_traits>
  6. #include <vector>
  7.  
  8. #if 0
  9. namespace std
  10. {
  11. 	template<class FwdIt, class C>
  12. 	back_insert_iterator<C> copy(
  13. 		FwdIt begin, FwdIt end, back_insert_iterator<C> it,
  14. 		forward_iterator_tag * =
  15. 		  static_cast<typename iterator_traits<FwdIt>::iterator_category *>(0))
  16. 	{
  17. 		struct It : public back_insert_iterator<C>
  18. 		{
  19. 			using back_insert_iterator<C>::container;
  20. 			static C &deref(C &c) { return  c; }
  21. 			static C &deref(C *c) { return *c; }
  22. 		};
  23. 		copy(begin, end, inserter(It::deref(static_cast<It &>(it).container),
  24. 					  It::deref(static_cast<It &>(it).container).end()));
  25. 		return it;
  26. 	}
  27.  
  28. 	template<class FwdIt, class C>
  29. 	typename enable_if<  // Only do this if it would be exception-safe!
  30. 		has_nothrow_copy_constructor<typename C::value_type>::value &&
  31. 		has_nothrow_assign<typename C::value_type>::value,
  32. 		insert_iterator<C>
  33. 	>::type copy(
  34. 		FwdIt const &begin, FwdIt const &end,
  35. 		insert_iterator<C> output,
  36. 		forward_iterator_tag * =                  // only forward iterators
  37. 		  static_cast<typename iterator_traits<FwdIt>::iterator_category *>(0))
  38. 	{
  39. 		struct It : public insert_iterator<C>
  40. 		{
  41. 			using insert_iterator<C>::container;  // protected -> public
  42. 			using insert_iterator<C>::iter;       // protected -> public
  43. 			static C &deref(C &c) { return  c; }
  44. 			static C &deref(C *c) { return *c; }
  45. 		};
  46. 		It &it(static_cast<It &>(output));
  47. 		typename C::iterator it_iter_end(It::deref(it.container).end());
  48. 		{
  49. 			// Convert iterators to offsets
  50. 			typename C::size_type const iter_end_off =
  51. 				std::distance(It::deref(it.container).begin(), it_iter_end);
  52. 			typename iterator_traits<typename C::iterator>::difference_type off
  53. 				= std::distance(It::deref(it.container).begin(), it.iter);
  54.  
  55. 			// Resize container
  56. 			It::deref(it.container).resize(
  57. 				It::deref(it.container).size() +
  58. 				static_cast<typename C::size_type>(std::distance(begin, end)));
  59.  
  60. 			// Renormalize, in case invalidated
  61. 			it.iter = It::deref(it.container).begin();
  62. 			std::advance(it.iter, off);
  63. 			it_iter_end = It::deref(it.container).begin();
  64. 			std::advance(it_iter_end, iter_end_off);
  65. 		}
  66. 		typename C::iterator result
  67. 		  = copy_backward(it.iter, it_iter_end, It::deref(it.container).end());
  68. 		copy_backward(begin, end, result);
  69. 		return inserter(It::deref(it.container), result);
  70. 	}
  71. }
  72. #endif
  73.  
  74. int main()
  75. {
  76. 	std::vector<unsigned char> x;
  77. 	x.resize(1000000);
  78. 	clock_t begin = clock();
  79. 	long long totalMS = 0;
  80. 	for (int i = 0; i < 100; i++)
  81. 	{
  82. 		std::vector<unsigned char> y; y.reserve(x.size());
  83. 		std::copy(x.begin(), x.end(), std::back_inserter(y));
  84. 	}
  85. 	clock_t end = clock();
  86. 	printf("%d\n", (int)((end - begin) * 1000 / CLOCKS_PER_SEC));
  87. }
Success #stdin #stdout 0.49s 2884KB
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https://ideone.com/pNhSw
language:
C++14 (gcc 8.3)
created:
13 years ago
visibility:
public

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