Hourglass using recursion

**nWeid1** · May 1st, 2012, 04:31 PM

I have to write a recursive program that makes an hourglass that suites the size of the user's input. For example, if the user types 4, this should print:

* * * *
 * * *
  * *
   *
  * *
 * * *
* * * *

and so far I got this far:

* * * *
* * *
* *
*
* *
* * *
* * * *

so I just need to figure out how to get the spaces but I'm not sure how to do this. Thanks for the help.

import java.util.InputMismatchException;
import java.util.Scanner;
 
public class Hourglass {
 
	public static void main(String[] args) {
 
		Scanner console = new Scanner(System.in);
		System.out.println("Enter an integer greater than or equal to 1");
		int n = 0;
		try {
			n = console.nextInt();
		} catch (InputMismatchException e) {
			e.getMessage();
		}
		if (n < 1) {
			System.out.println("Invalid input");
		} else {
			System.out.println("");
			hourglass(n, 0);
			System.out.println("");
		}
 
	}
 
	public static void hourglass(int n, int count) {
		recursion(n, count);
		if(n > 1) {
			hourglass(n-1, count);
			recursion(n, count);
		}
	}
 
	public static void recursion(int n, int count) {
		System.out.print("* ");
		if (n > 1)
			recursion(n - 1, count);
		else
			System.out.println();
	}
}

**andreas90** · May 1st, 2012, 04:38 PM

Hello nWeid1!
I can't see the difference between the output as it should be and the one you actually get. What do you mean by "figure out how to get the spaces"?

**nWeid1** · May 1st, 2012, 04:48 PM

I just updated it. for some reason it won't display the spaces unless its

**andreas90** · May 1st, 2012, 05:02 PM

Where in your code do you have these spaces? I can only see two print statements in the recursion code -one for stars and the other for an empty line.

**nWeid1** · May 1st, 2012, 05:07 PM

Well, I don't. I don't know where to implement the code to have them print out properly which is my problem.

**andreas90** · May 1st, 2012, 05:15 PM

For this kind of problems you should write down the logic of your program and *test* it in a piece of paper before you implement code.
Also, what is the variable count? Did you think of a way to use it to accomplish what you want?

**nWeid1** · May 1st, 2012, 05:35 PM

Yeah I figured I could use count so that every line of stars there should add 1 space before the next line of stars. I also thought of creating a separate method just for the spaces but I don't know if that will work out.

**andreas90** · May 1st, 2012, 05:50 PM

Originally Posted by nWeid1

Yeah I figured I could use count so that every line of stars there should add 1 space before the next line of stars. I also thought of creating a separate method just for the spaces but I don't know if that will work out.

You should try it and see what is happening. But again I suggest you writing down the logicof the program.
Hint: not sure if you are allowed to use them, but for loops is a very common approach in such kind of problems.

**nWeid1** · May 1st, 2012, 05:57 PM

Ok I'll try to write it down. And yeah my teacher said we can't use any for loops, hence the reason I'm using recursion in the first place

**copeg** · May 1st, 2012, 06:56 PM

This thread has been cross posted here:

http://www.java-forums.org/new-java/59150-hourglass-using-recursion.html

Although cross posting is allowed, for everyone's benefit, please read:

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**Darryl.Burke** · May 1st, 2012, 10:30 PM

One more: Hourglass Using Recursion - Java | Dream.In.Code

db

edit The OP is presently throwing a temper tantrum on the thread linked by copeg

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