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  1. #include <iostream>
  2. #include <cmath>
  3. using namespace std;
  4.  
  5. bool is_prime(int m){
  6. 	if (m <= 1) return false;
  7. 	if (m <= 3) return true;
  8. 	if (m % 2 == 0 || m % 3 == 0) return false;
  9. 	int limit = sqrt(m);
  10. 	for (int i = 5; i <= limit; i += 6){
  11. 		if (m % i == 0) return false;
  12. 		if (m % (i+2) == 0) return false;
  13. 	}
  14. 	return true;
  15. }
  16.  
  17. int prime_count(int k){
  18. 	if (k <= 1) return 0;
  19. 	if (k == 2) return 1;
  20. 	int p_c = 1;
  21. 	for (int i = 3; i <= k; i += 2){
  22. 		p_c = p_c + is_prime(i);
  23. 	}
  24. 	return p_c;
  25. }
  26.  
  27. int main() {
  28. 	int n;
  29. 	cin >> n;
  30. 	int t [2*n];
  31. 	for (int i = 0; i < n * 2; i++){
  32. 		cin >> t[i];
  33. 	}
  34. 	for (int j = 0; j < 2 * n; j += 2){
  35. 	int a = t[j];
  36. 	int b = t[j + 1];
  37. 	int k = prime_count(b) - prime_count(a - 1);
  38. 	cout << k << endl;
  39. }
  40. 	return 0;
  41. }
Success #stdin #stdout 0.01s 5276KB
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https://ideone.com/TTzHPI
language:
C++ (gcc 8.3)
created:
2 days ago
visibility:
public

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