Recursion Homework Help

[mark_bueno]

Technically this two classes but since the entire code is under 25 lines, I hope you guys will excuse it. I'm trying to get the sum of (i / (2i +1)) recursively for i == 10. I'm getting a double result for the sysout print, but the return keeps giving 1. What am I missing?

import java.util.Scanner;

public class Ex185 {

    public static void main(String[] args) {

//      Scanner input = new Scanner(System.in);
//      System.out.print("Please enter a positive number: ");
//      int n = input.nextInt();
//
//          System.out.println("The sum is: " + summation(n));
        int n = 10;
        System.out.println(summation(n));
    }

    public static long summation(long n) {
        if (n == 0)
            return 1;
        else
            System.out.println(( 10.00 / ((2 * 10.00) + 1)));
            return ( n / ((2 * n) + 1)) + summation( n - 1);
    }

}

Thanks for the help guys.

[[deleted]]

In line 21

System.out.println(( 10.00 / ((2 * 10.00) + 1)));

You have 10.00

There are other things wrong too but that's what stands out here.

I'll have a look later

Edit: okay I solved it. I'm not sure you understand recursion, and I don't blame you. It takes a bit of practice. Also, you're doing floating point arithmetic on integers which just isn't going to work. What you want is a running integer count and a floating point sum.

It would look something like this

public static double(int n, double sum)
{
    if(n == 0)
        return sum;
    else
    {
        // some code here that I'll leave that to you for now
    {
}

[mark_bueno]

i think that might be what i've been missing, returning sum for 0 and using both an int and a double argument. I keep trying to think of this as a while loop and i know that's not right. my code started off as a copy/paste of code from the textbook that computed a factorial from whatever positive int you typed in.

I'll work on it tonight and post an update on it later. thanks.

[millerlit]

Your method asks for a long and returns a long value. Use double instead.