Print BTree by level

问题

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;
    }

回答1:

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).

回答2:

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
}

来源：https://stackoverflow.com/questions/5890960/print-btree-by-level