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Thread: Help in understanding this recursive method

  1. #1
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    Default Help in understanding this recursive method

    We are learning recursion in my intro to Java class, and I am having a hard time understanding how the method in the example given works. Any explanation as to what is happening when the method is called would be appreciated.

    Here is the code:

    public class Hanoi
     
    private int n;
    private int pegA;
    private int pegB;
     
    public Hanoi(int in_n, int in_pegA, int in_pegB)
    {
        n = in_n;
        pegA = in_pegA;
        pegB = in_pegB;
    }
     
    public void makemoves()
    {
        if (n==1)
            System.out.format("%d ==> %d%n", pegA, pegB)
        else
        { 
             int otherPeg = 6 - pegA - pegB; // 1 + 2 + 3 =6
             Hanoi firstmove = new Hanoi (n-1, pegA, otherPeg);
             firstmove.makemoves();
             System.out.format("%d ==> %d%n", pegA, pegB);
             Hanoi secondmove = new Hanoi (n-1, otherPeg, pegB);
             secondmove.makemoves();
        }
    }
    }


  2. #2
    Super Moderator curmudgeon's Avatar
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    Default Re: Help in understanding this recursive method

    Cross-posted here. Most appreciate it if when you cross-post a question, you provide links to the cross-post so we can avoid duplicating effort that's already been exerted. We're volunteers and value our free time as much as you do.

  3. #3
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    Default Re: Help in understanding this recursive method

    @curmudgeon

    Will do.

    ~~~~

    So what order would the code execute in.

    Obviously it would first run

    Hanoi firstmove = new Hanoi (n-1, pegA, otherPeg);
             firstmove.makemoves();

    but then would it run Hanoi firstmove = new Hanoi (n-1, pegA, otherPeg) again, or would it run System.out.print?

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