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Thread: Complexity problem

  1. #1
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    Default Complexity problem

    I'm trying solve a problem which I have been able to code on a smaller scale though as soon as I start imputing larger values the time it takes increases considerably to the point where the final solution may take me a lifetime to find out.

    The problem is Project Euler | Problem 12, I don't want the solution rather just guidance on a considerably more efficient collection type which may aid me.

    The following is my own code:
    public class abc{
      public static void main(String[] args){
    	 for(int j=1;j<1000;j++){
    	  List<Integer>ar = new ArrayList<Integer>();
    	 for(int i=1;i<triangle(j)+1;i++){
          if(triangle(j)%i==0){
        	  ar.add(i);
          }
       	 }
     
    	 if(ar.size()>5){
    	 System.out.println(triangle(j));
    	 break;
    	 }	
    	 }
    	 }
     
     
      public static int triangle(int num){
    	  if(num==1){
    		  return 1;
    	  }
    	  return num +triangle(num-1);
      }
      }
    I need to replace the 5 with a 500 to find the solution.


  2. #2
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    Default Re: Complexity problem

    Do only what is necessary to answer the question. Simplify your program to something like:

    1. Find the next triangle number
    2. Find the number of factors in the triangle number
    3 Report the first triangle number to have over 500 factors and stop, OR
    4. Goto 1

    My solution is simpler than yours and could be simplified some, but finding the answer takes a looooong time.

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