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  1. #include <algorithm>
  2. #include <iostream>
  3. #include <iterator>
  4. #include <vector>
  5. using namespace std;
  6.  
  7. class Generator: public std::iterator<std::forward_iterator_tag, size_t> {
  8. public:
  9. 	Generator(size_t init): result(init) {
  10. 		while (init > 0) {
  11. 			array.push_back(init % 10);
  12. 			init /= 10;
  13. 		}
  14. 		std::reverse(array.begin(), array.end());
  15. 	}
  16.  
  17. 	Generator& operator++() {
  18. 		this->increment();
  19. 		this->convert();
  20. 		return *this;
  21. 	}
  22.  
  23. 	Generator& operator++(int) { Generator tmp(*this); ++tmp; return *this; }
  24.  
  25. 	size_t& operator*() { return result; }
  26. 	size_t const& operator*() const { return result; }
  27.  
  28. 	size_t* operator->() { return &result; }
  29. 	size_t const* operator->() const { return &result; }
  30.  
  31. 	bool operator==(Generator const& other) {
  32. 		return result == other.result;
  33. 	}
  34.  
  35. 	bool operator!=(Generator const& other) {
  36. 		return result != other.result;
  37. 	}
  38.  
  39. private:
  40. 	void convert() {
  41. 		result = 0;
  42. 		for (auto e: array) { result *= 10; result += e; }
  43. 	}
  44.  
  45. 	void increment() {
  46. 		typedef std::vector<uint8_t>::const_reverse_iterator It;
  47.  
  48. 		std::vector<uint8_t> r;
  49. 		bool carry = true;
  50.  
  51. 		for (It it = array.rbegin(), end = array.rend(); it != end; ++it) {
  52. 			uint8_t e = *it;
  53. 			if (carry) { e += 1; carry = false; }
  54. 			if (e > 6) { e = 4; carry = true; }
  55. 			r.push_back(e);
  56. 		}
  57.  
  58. 		if (carry) { r.push_back(4); }
  59.  
  60. 		array.assign(r.rbegin(), r.rend());
  61. 	}
  62.  
  63. 	size_t result;
  64.  
  65. 	std::vector<uint8_t> array;
  66. }; // class Generator
  67.  
  68. int main() {
  69. 	size_t i = 0;
  70. 	for (Generator it(4), end(666555); it != end; ++it) {
  71. 		i += *it;
  72. 	}
  73. 	std::cout << i << "\n";
  74. 	return 0;
  75. }
Success #stdin #stdout 0s 3276KB
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409632209
https://ideone.com/hi5fhd
language:
C++14 (gcc 8.3)
created:
8 years ago
visibility:
public

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