CODEWITHSUNDEEP
javascript
Jabbath
Jabbath

Reputation: 334

Euler Challenge 3 Javascript: Solution Gives Correct Answer but then I get stuck in an infinite loop

I was trying out the 3rd challenge in the Euler project and I wrote this code to try and solve it.The idea is to find the highest prime factor of 600851475143. After a few popups from Winscript I get the right answer, but then my cpu jumps to 25% and I get nothing else from Winscript leading me to believe something is causing it to go into an infinite loop. Can anyone spot what the problem is? 

var isprime = function(n)
{
var s= Math.sqrt(n);
for(i=2;i<=s;i++)
 {
  if(n%i===0)
  {
      return false;
  }
 }
    return true;
};
var largest = 0;
var q=0;
while(q<(600851475143/4))
{

    if(600851475143%q===0)
    {
        if(q>largest)
        {
        if(isprime(q))
        {
        largest=q;
        WScript.Echo(largest);
        }
        }

        var d = 600851475143/q;


        if(d>largest)
        {
        if(isprime(d))
        {
        largest = d;
        WScript.Echo(largest);
        }
        }

    }
    q+=1;
 }
     WScript.Echo(largest);

Upvotes: 0

Views: 89

Answers (1)

Pointy
Pointy

Reputation: 413818

Once you've found the largest factor, the loop will continue to run, and run, and run, until it has reached the end condition — when q is 150212868785. One hundred and fifty trillion iterations takes a while.

Upvotes: 1

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