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  1. #include <iostream>
  2. #include <chrono>
  3.  
  4. #define sqr(x) ((x) * (x))
  5.  
  6. using namespace std;
  7.  
  8. auto start = chrono::steady_clock::now();
  9.  
  10. int primes[1000000] = {2};
  11. int count = 0;
  12.  
  13. int main() {
  14.     for (int n = 3; n < 1000000; n += 2) {
  15.         bool is_prime = true;
  16.         for (int i = 0; sqr(primes[i]) <= n; i++) {
  17.             if (n % primes[i] == 0) {
  18.                 is_prime = false;
  19.                 break;
  20.             }
  21.         }
  22.         if (is_prime) {
  23.             primes[count++] = n;
  24.         }
  25.     }
  26.  
  27.     cout << count << endl;
  28.  
  29.     auto elapsed = chrono::duration_cast<chrono::milliseconds>(
  30.     	chrono::steady_clock::now( ) - start
  31.     	);
  32.  
  33.     std::cout << "milliseconds since start: " << elapsed.count() << endl;
  34.  
  35.     return 0;
  36. }
  37.  
  38.  
Success #stdin #stdout 0.08s 5456KB
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stdin
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Standard input is empty
stdout
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78497
milliseconds since start: 70
https://ideone.com/AtoLIT
language:
C++ (gcc 8.3)
created:
4 years ago
visibility:
public

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