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  1. #include <iostream>
  2. #include <vector>
  3. #include <algorithm>
  4.  
  5. class SquarePushBackIterator: public std::iterator<std::output_iterator_tag,int>
  6. {
  7. 	std::vector<int>& dst;
  8. public:
  9. 	SquarePushBackIterator(std::vector<int>& dst) : dst(dst) {}
  10. 	// These just return references to the iterator.
  11. 	// The only operation that matters is assignment.
  12. 	SquarePushBackIterator& operator*()     { return *this; }
  13. 	SquarePushBackIterator& operator++()    { return *this; }
  14. 	SquarePushBackIterator& operator++(int) { return *this; }
  15.  
  16. 	// The assignment squares and inserts into the destination.
  17. 	void operator=(int val)
  18. 	{
  19. 		dst.push_back(val * val);
  20. 	}
  21. };
  22.  
  23. void mergeSortedArray(std::vector<int>& data)
  24. {
  25.  
  26. 	// Find the iterator range for the positive values.
  27. 	using iter = std::vector<int>::const_iterator;
  28. 	iter  endPositive = std::end(data);
  29. 	iter  loopPositive = std::find_if(std::begin(data), std::end(data),
  30. 		[](int val) {return val >= 0; });
  31.  
  32. 	// Find the iterator range for the negative values.
  33. 	using reve = std::reverse_iterator<iter>;
  34. 	reve  endNegative = reve(std::begin(data));
  35. 	reve  loopNegative = reve(loopPositive);
  36.  
  37. 	// Create an array to put the results into.
  38. 	std::vector<int>  result;
  39. 	result.reserve(data.size());
  40.  
  41. 	// Perform a standard merge
  42. 	std::merge(loopPositive, endPositive, loopNegative, endNegative,
  43. 		SquarePushBackIterator(result),
  44. 		[](int val1, int val2){return std::abs(val1) < std::abs(val2); });
  45.  
  46. 	// Use move assignment to put the result in the output vector.
  47. 	// Alternatively we could return an array by value.
  48. 	data = std::move(result);
  49. }
  50.  
  51. int main()
  52. {
  53. 	std::vector<int> arr={ -3, -2, 0, 4, 5, 8 };
  54.  
  55. 	mergeSortedArray(arr);
  56.  
  57. 	for (const auto& i : arr)
  58. 	{
  59. 		std::cout << i << ' ';
  60. 	}
  61. }
Success #stdin #stdout 0s 3432KB
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0 4 9 16 25 64
https://ideone.com/RWUnvj
language:
C++14 (gcc 8.3)
created:
9 years ago
visibility:
public

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