Sep 6

[Python,Algorithms] Fast Modular exponentiation script

Algorithms, Python algorithm, code, exponentiation, Python Add Comment (3)

If we want to know the last ten digits of number aⁿ – we have to evaluate expression aⁿ mod 10¹⁰. Using brute force approach, we have to do O(n) ( If you don’t understand big „O” notation, visit: Big O notation – it’s VERY important) multiplications and modulo divisions. When n is greater than 10⁹, it will take a lot of time. Fortunately, we can use more „mathematical” approach, which has O(log n) complexity. Read More

Sep 2

[PHP] Execution/evaluation of code from variable

PHP code, PHP Add Comment (3)

In PHP we can use function eval in order to evaluate given variable (string) as PHP code:

<? 
$var = 'for ($i=0;$i<5;$i++)
{
	echo $i.\'<br>\';
}';
eval($var);
?>

output:

0
1
2
3
4