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Thread: Sum of series program logical error

  1. #1
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    Question Sum of series program logical error

    This program is supposed to calculate:
    S= 2! -4! +6! -8! ..n terms

    public class Series7
    {
    int sum, i, term, j, prod;
    public void main(int n)
    {
    sum = 0;
    term=2;
    prod = 1;
    for (i=1;i<=n;i++)
    {
    for(j=term;j>1;j--)
    prod *= j;

    term += 2;
    if(i%2==0)
    sum -= prod;
    else
    sum += prod;

    }
    System.out.println("The sum is "+sum);
    }
    }


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    Default Re: Sum of series program logical error

    What does it do instead? Do you have a question?
    Useful links: How to Ask Questions the Smart Way | Use Code Tags | Java Tutorials
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    Default Re: Sum of series program logical error

    You have a ton of problems with syntax but that aside your logic problems stems from messy seperation of what each loop does.

    Outer loop: adds 2 to the term, adds the fac result to the output sum.
    Inner loop: Fac'ing the term.

    Im not sure you are fac'ing right. Try using recursion as it brings beautiful solution to fac'ing.

    	public void myFunc(int n){
    		int sum = 0;
    		int term = 2;
     
    		for (int i = 1; i <= n ; i++){
    			if(i % 2 == 0)
    			{
    				sum -= myFac(term);
    			} else {
    				sum += myFac(term);
    			}
    			term += 2;
    		}
    		System.out.println(sum);
    	}

    Remember to use highlight tags, or you code is unreadable
    Last edited by Johannes; August 12th, 2011 at 11:36 AM.

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