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Thread: looping problem in Hailstrom program

  1. #1
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    Default looping problem in Hailstrom program

    Hello, I just started doing an online tutorial to learn some java and I'm stumped on solving this Hailstorm Problem. The problem is an old math phenomenon where no matter what number you start with you will end at the number 1. If the number is even you divide it by two and if its odd you compute 3n + 1 (n being the number) and you continue to do it until you reach 1. So here was my attempt at solving it:

    import acm.program.*;
     
    public class Hailstone extends ConsoleProgram {
     
    	public void run() {
    		int n = readInt ("Enter a number: ");
    		int turns = 1;
    		while (n != 1) {
    			if ((n % 2) == 0){
    				numEven(n);	
    			} else {
    				numOdd(n);
    			}
    			turns++;
    		}
    		println ("The process took " + turns + " to reach 1.");
    	}
     
    	// numEven computes the answer if n is even.
    	private int numEven (int n) {
    		int j = n/2;
    		println (n + " is even so I take half: " + j);
    		return j;
    	}
     
    	// numOdd computes the answer if n is odd.
    	private int numOdd (int n) {
    		int k = (int)(n * 3) + 1;
    		println (n + " is odd, so I make 3n + 1: "+ k);
    		return k;
    	}
     
    }

    The problem being that its looping indefinitely after it solves the first even or odd computation and doesn't put the returned value back into the original n for the second loop. Let me know if you think of anything to solve this. Thanks.


  2. #2
    mmm.. coffee JavaPF's Avatar
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    Default Re: Hailstorm problem from a new programmer.

    Hello JonnyBoy and welcome to the Java Programming Forums

    I need to be able to compile this code to test it out. Could you please include the ConsoleProgram class?
    Please use [highlight=Java] code [/highlight] tags when posting your code.
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    Default Re: Hailstorm problem from a new programmer.

    So, basically I looked in the other folder that came with the assignment, and ConsoleProgram is a class that has a bunch of other things stringed into it that I think are too complicated to try to give to you. Instead, if you still wanted to try to compile it go here: CS106A Programming Methodology and download the second assignment, import it as a project, and copy my code into the Hailstorm file.
    This got a little more complicated than I had expected so if its too much work don't sweat it. Unfortunately I don't actually go to stanford, but am just taking the class on itunes otherwise i'd just ask the teacher for help .

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    Default Re: Hailstorm problem from a new programmer.

    numOdd(n);
    should become
    n = numOdd(n);

    and the same for even,

    Regards,
    Chris

  5. The Following User Says Thank You to Freaky Chris For This Useful Post:

    JonnyBoy (May 8th, 2009)

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    Default Re: Hailstorm problem from a new programmer.

    Sweet, that's the ticket! Thanks a bunch Chris.

  7. #6
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    Default Re: Hailstorm problem from a new programmer.

    Your welcome, glad I could help.

    Regards,
    Chris

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