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  1.  
  2. #include <unordered_set>
  3.  
  4. struct Point {
  5.     int X;
  6.     int Y;
  7.  
  8.     Point() : X(0), Y(0) {};
  9.     Point(const int& x, const int& y) : X(x), Y(y) {};
  10.     Point(const Point& other){
  11.         X = other.X;
  12.         Y = other.Y;
  13.     };
  14.  
  15.     Point& operator=(const Point& other) {
  16.         X = other.X;
  17.         Y = other.Y;
  18.         return *this;
  19.     };
  20.  
  21.     bool operator==(const Point& other) {
  22.         if (X == other.X && Y == other.Y)
  23.             return true;
  24.         return false;
  25.     };
  26.  
  27.     bool operator<(const Point& other) {
  28.         if (X < other.X )
  29.             return true;
  30.         else if (X == other.X && Y == other.Y)
  31.             return true;
  32.  
  33.         return false;
  34.     };
  35.  
  36. 	// this could be moved in to std::hash<Point>::operator()
  37.     size_t operator()(const Point& pointToHash) const noexcept {
  38.         size_t hash = pointToHash.X + 10 * pointToHash.Y;
  39.         return hash;
  40.     };
  41.  
  42. };
  43.  
  44. namespace std {
  45. 	template<> struct hash<Point>
  46. 	{
  47. 		std::size_t	operator()(const Point& p) const noexcept
  48. 		{
  49. 			return p(p);
  50. 		}
  51. 	};
  52. }
  53.  
  54. int main()
  55. {
  56.     // no need to specify the hasher if std::hash<Point> exists
  57. 	std::unordered_set<Point> p;
  58. 	return 0;
  59. }
Success #stdin #stdout 0s 4316KB
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https://ideone.com/OOdbFx
language:
C++14 (gcc 8.3)
created:
5 years ago
visibility:
public

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