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  1. using System;
  2. using System.Collections.Generic;
  3.  
  4. public class Test
  5. {
  6. 	public static List<int> get_primes (int n) {
  7. 		// is_prime[i] == true, если i -- простое число
  8. 		bool[] is_prime = new bool[n+1];
  9. 		for (int i = 2; i <= n; ++i) is_prime[i] = true;
  10. 		// primes будет содержать все простые числа на отрезке от 1 до n
  11. 		List<int> primes = new List<int>();
  12. 		// Алгоритм Решето Эратосфена
  13. 		for (int i=2; i<=n; ++i)
  14. 		    if (is_prime[i]) {
  15. 		    	primes.Add(i);
  16. 		        if (i * i <= n)
  17. 		            for (int j=i*i; j<=n; j+=i)
  18. 		                is_prime[j] = false;
  19. 		    }
  20. 		return primes;
  21. 	}
  22.  
  23. 	public static void Main()
  24. 	{
  25. 		List<int> primes = get_primes(20);
  26. 		Console.WriteLine(string.Join(", ", primes));
  27. 	}
  28. }
  29.  
Success #stdin #stdout 0.04s 23896KB
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stdin
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Standard input is empty
stdout
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2, 3, 5, 7, 11, 13, 17, 19
https://ideone.com/s1UWB2
language:
C# (gmcs 5.20.1)
created:
7 years ago
visibility:
public

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