Print BTree by level

Question

I am trying to create a Java applet that animates a BTree. I have code to create the tree but now I am trying to display it. I thought the easiest way would be to print by level but I can't figure out how. The below code is the constructor for my nodes. Also, if anyone has a better suggestion for displaying my tree I would appreciate it.

    /***********************************************************************
 * Class BTNode
 * The BTNode is nothing else than a Node in the BTree. This nodes can be
 * greater or smaller it depends on the users order.
 **/

class BTNode {
    int order=0;
    int nKey=0;         // number of keys stored in node
    KeyNode kArray[];       // array where keys are stored
    BTNode btnArray[];  // array where references to the next BTNodes is stored
    boolean isLeaf;     // is the btnode a leaf
    BTNode parent;      // link to the parent node

    /**
       * BTNode(int order, BTNode parent);
       * Constructor, creats a empty node with the given order and parent
       **/
    BTNode(int order, BTNode parent) {
        this.order = order;
        this.parent = parent;
        kArray = new KeyNode[2 * order - 1];
        btnArray = new BTNode[2 * order];
        isLeaf = true;
    }

score 3 · Accepted Answer · answered May 04 '11 at 23:49

3

You want to perform a level-order traversal of the tree. If space is not a limiting factor, I'd suggest building a queue of nodes that you wish to visit next (adding their child nodes onto the end of the queue upon visit).

answered May 04 '11 at 23:49

eggyal

122,705
18
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1

Thanks for the idea. I ended up using two queues (adding all the children of the nodes in the first queue to the second queue and then vice versa) this way I could keep track of when a line break was needed. – kfeeney May 05 '11 at 06:15

score 1 · Answer 2 · answered May 04 '11 at 23:53

1

I would also recommend a level order transversal. Here is some sudocode for it:

Add root to queue
while queue is not empty
{
    r = queue.top()
    process r
    remove r from queue
    add r's non-NULL children to the queue
}

answered May 04 '11 at 23:53

matzahboy

3,004
20
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Print BTree by level

2 Answers2

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