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Prime number detector: brute force method
By Sparky | December 6, 2005
Tonight I continued my development efforts and implemented a simple brute force algorithm that detects if a given number is prime. You can see it in action or check out the code I used:
$max = (int)(sqrt($totest) + 1); //set the max value to test
$isprime = true; //initialize the $isprime variable
for ($i = 2; $i <= $max; $i++) { //for loop from 2 to $max
//Determine if $totest is divisible by $i
if (fmod($totest, $i) == 0) { //is there a remainder?
$isprime = false; //the number is not prime
$i = $max; //exit the loop
}
}
Neat huh? Not too complicated but fun to do. Next I’m going to implement a sieve algorithm to determine if a series of numbers is prime or not.
Topics: Development, Technology |