java - How can I reduce run time Q12 Project Euler -

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my code takes way long run. i've tried loop way large number , loop ip find it's sum loop check divisors.how optimise it?

public class q12 {      public static void main(string[] args)      {          int answer=5;         boolean check=false;         int sum=0;         int counter=0;         int kk=0;         while(check==false)         {             loop:             for(int i=1;i<50000000;i++)             {                 sum=0;                 counter=0;                  for(int j=0;j<i;j++)                 {                     sum=j+sum;                 }                  for(int k=1;k<sum;k++)                 {                     if(sum%k==0)                     {                         counter=counter+1;                     }                  }                  if(counter>=501)                 {                     check=true;                     break loop;                 }               }           }        }  }

thanks

  1. it's not obvious yours code supposed do, i'm doubt can optimize there...

  2. this portion:

    check=true; break loop;

    breaks execution , jumps to

    loop: for(int i=1;i<50000000;i++)

    which run inner loop 50000000 iterations again, after check evaluated. intended behaviour?

  3. here:

    sum=0; counter=0;  for(int j=0;j<i;j++) {     sum=j+sum; }

    you can use caching. like:

    long[] precalc = new long[50000000];  int answer=5; boolean check=false; int sum=0; int counter=0; int kk=0; while(check==false) {     loop:     for(int i=1;i<50000000;i++)     {         sum = precalc [i];         if (sum == 0) {             precalc[i] = sum = (precalc[i - 1] + i);         }          counter=0;          ...

  4. also suggest use long-s instead of int-s, there possible arithmetic overflow.


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