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  1. #include <iostream>
  2. #include <vector>
  3. using namespace std;
  4.  
  5. vector<int> sosu;
  6. bool isPrime[1000002];
  7.  
  8. void check(int num){
  9. 	int sum = num + num;
  10. 	while(sum <= 1000000){
  11. 		isPrime[sum] = false;
  12. 		sum += num;
  13. 	}
  14. }
  15.  
  16. int main() {
  17.  
  18. 	fill_n(isPrime,1000002,1);
  19.  
  20. 	for(int i = 2; i <= 1000000; i++){
  21. 		if(!isPrime[i]) continue;
  22. 		sosu.push_back(i);
  23. 		check(i);
  24. 	//	printf("%d ",i);
  25. 	}
  26.  
  27. 	int T;
  28.  
  29. 	scanf("%d",&T);
  30.  
  31. 	for(int t = 0; t < T; t++){
  32. 		int n;
  33. 		scanf("%d",&n);
  34. 		int cnt = 0;
  35.  
  36. 		for(int a = 2; a <= n/2; a++){
  37. 			int b = n - a;
  38. 			if(isPrime[a] && isPrime[b]){
  39. 				cnt++;
  40. 			}
  41. 		}
  42. 		printf("%d\n",cnt);
  43.  
  44.  
  45. 	}
  46.  
  47.  
  48.  
  49. 	return 0;
  50. }
Success #stdin #stdout 0.01s 4800KB
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https://ideone.com/Um9044
language:
C++14 (clang 8.0)
created:
4 years ago
visibility:
public

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