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Project euler 7

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  1. <?php
  2.  
  3. /**
  4. cobra90nj@cobra90nj:~/Scrivania$ time php ll.php
  5. 104760
  6. real	0m46.014s
  7. user	0m42.267s
  8. sys	0m0.056s
  9. */
  10.  
  11. function isPrime($num) 
  12. {
  13. 	if ($num == 2 || $num == 3) { return 1; }
  14. 	if (!($num%2) || $num<1)    { return 0; }
  15.  
  16. 	for ($n = 3; $n <= $num/2; $n += 2) {
  17. 		if (!($num%$n)) {
  18. 			return 0;
  19. 		}
  20. 	}
  21.  
  22. 	return 1;
  23. }
  24.  
  25. $obb  = 1; 
  26. $ispr = 4;
  27.  
  28. while ($obb < 10001) {
  29.  
  30. 	if (isPrime($ispr)) {
  31. 		 $obb++;
  32. 		 $ispr++;
  33.  	}
  34.  	else {
  35.  		$ispr++;
  36. 	}
  37. }
  38.  
  39. echo $ispr;

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