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  1. #include <iostream>
  2. #include <algorithm>
  3. #include <vector>
  4. #include <unordered_set>
  5. #include <cstdlib>
  6. #include <ctime>
  7. #include <cassert>
  8.  
  9. typedef unsigned long long ull;
  10. typedef std::pair<int,ull> Hash;
  11.  
  12. struct getHash {
  13. public:
  14. 	template <typename T, typename U>
  15. 	std::size_t operator()(const std::pair<T, U> &x) const
  16. 	{
  17. 		return std::hash<T>()(x.first) ^ std::hash<U>()(x.second);
  18. 	}
  19. };
  20.  
  21. ull rand_ull() {
  22. 	ull res = 0;
  23. 	for (int i = 0; i < 6; ++i) {
  24. 		(res *= 1000) += (std::rand() % 1000);
  25. 	}
  26. 	return res;
  27. }
  28.  
  29. int main() {
  30. 	std::srand(std::time(0));
  31.  
  32. 	const int n = (int)4e6;
  33.  
  34. 	std::vector<Hash> array(n);
  35.  
  36. 	for (auto& it : array) {
  37. 		it = std::make_pair(std::rand() % (int)1e9, rand_ull());
  38. 	}
  39.  
  40. 	std::vector<Hash> queries(n);
  41.  
  42. 	for (auto& it : queries) {
  43. 		it = std::make_pair(std::rand() % (int)1e9, rand_ull());
  44. 	}
  45.  
  46. 	double t = clock();
  47.  
  48. 	std::unordered_set<Hash, getHash> hashtable;
  49.  
  50. 	for (auto it : array) {
  51. 		hashtable.insert(it);
  52. 	}
  53.  
  54. 	int count1 = 0;
  55.  
  56. 	for (auto hash : queries) {
  57. 		count1 += hashtable.find(hash) != hashtable.end();
  58. 	}
  59.  
  60. 	double time1 = (clock() - t) / CLOCKS_PER_SEC;
  61.  
  62. 	t = clock();
  63.  
  64. 	std::sort(array.begin(), array.end());
  65.  
  66. 	int count2 = 0;
  67.  
  68. 	for (auto hash : queries) {
  69. 		count2 += std::binary_search(array.begin(), array.end(), hash);
  70. 	}
  71.  
  72. 	double time2 = (clock() - t) / CLOCKS_PER_SEC;
  73.  
  74. 	assert(count1 == count2);
  75.  
  76. 	fprintf(stdout, "size & queries = %d\n", n);
  77. 	fprintf(stdout, "     hashtable = %0.3fs\n", time1);
  78. 	fprintf(stdout, "sort+binsearch = %0.3fs\n", time2);
  79.  
  80. 	return 0;
  81. }
Success #stdin #stdout 4.47s 349304KB
comments (?)
stdin 
Standard input is empty
stdout 
size & queries = 4000000
     hashtable = 2.074s
sort+binsearch = 1.621s
https://ideone.com/W18tw5
language:
C++14 (gcc 8.3)
created:
6 years ago
visibility:
public

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