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  1. #include <vector>
  2. #include <cstdio>
  3. #include <ctime>
  4. #include <algorithm>
  5. #include <iterator>
  6. #include <utility>
  7.  
  8. using namespace std;
  9.  
  10. int main() {
  11.     int n = 100000,
  12. 		dummy = -1,
  13. 		n_remove_items = 10000;
  14.  
  15. 	vector<int> a(n, dummy);
  16. 	vector<int> b(n, dummy);
  17. 	vector<int> c;
  18.  
  19.     clock_t start = clock(); {
  20. 		random_shuffle(begin(a), end(a));
  21. 		for (int i = 0; i < n_remove_items; i++) {
  22. 			a.erase(begin(a));
  23. 		}
  24. 	} clock_t end = clock();
  25.     printf("a->size() = %d, %fsec.\n", a.size(), (double)(end - start) / CLOCKS_PER_SEC);
  26.  
  27. 	start = clock(); {
  28. 		for (int i = 0; i < n_remove_items; i++) {
  29. 			int index = rand() & b.size();
  30. 			b[index] = 0;
  31. 		}
  32. 		copy_if(begin(b), std::end(b), back_inserter(c), // XXX : duplication name(end)
  33. 			[&dummy](int x) {
  34. 				return x == dummy;
  35. 			});
  36. 		b = move(c);
  37. 	} end = clock();
  38.     printf("b->size() = %d, %fsec.\n", b.size(), (double)(end - start) / CLOCKS_PER_SEC);
  39.  
  40.     return 0;
  41. }
Success #stdin #stdout 0.84s 3228KB
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Standard input is empty
stdout
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a->size() = 90000, 0.843895sec.
b->size() = 99937, 0.001664sec.
https://ideone.com/HSRAZ0
language:
C++14 (gcc 8.3)
created:
9 years ago
visibility:
public

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