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  1. #include <iostream>
  2. #include <unordered_set>
  3.  
  4. namespace std {
  5. 	template<>
  6. 	struct hash<unordered_multiset<int>> {
  7. 		typedef unordered_multiset<int> argument_type;
  8. 		typedef std::size_t result_type;
  9.  
  10. 		const result_type BASE =  static_cast<result_type>(0xA67);
  11.  
  12. 		result_type log_pow(result_type ex) const
  13. 		{
  14. 		    result_type res = 1;
  15. 		    result_type base = BASE;
  16. 		    while (ex > 0)
  17. 		    {
  18. 		        if (ex % 2)
  19. 		            res = res * base;
  20. 		        base *= base;
  21. 		        ex /= 2;
  22. 		    }
  23. 		    return res;
  24. 		}
  25.  
  26. 		result_type operator()(argument_type const & val) const {
  27. 			result_type h = 0;
  28. 			for (const int& el : val) {
  29. 				h += log_pow(el);
  30. 			}
  31. 			return h;
  32. 		}
  33. 	};
  34. };
  35.  
  36. 	int main() {
  37. 		std::unordered_set<std::unordered_multiset<int>> mySet;
  38. 		std::unordered_multiset<int> set1{1,2,3,4};
  39. 		std::unordered_multiset<int> set2{1,1,2,2,3,3,4,4};
  40. 		std::cout << "Hash 1: " << std::hash<std::unordered_multiset<int>>()(set1) << std::endl;
  41. 		std::cout << "Hash 2: " << std::hash<std::unordered_multiset<int>>()(set2) << std::endl;
  42. 		return 0;
  43. 	}
Success #stdin #stdout 0s 3460KB
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Standard input is empty
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Hash 1: 2290886192
Hash 2: 286805088
https://ideone.com/oG0ZIX
language:
C++14 (gcc 8.3)
created:
8 years ago
visibility:
public

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