按层遍历二叉查找树

/**
 * Created by elvalad on 2014/12/5.
 * 按层遍历二叉查找树
 */
import java.util.Iterator;
import java.util.LinkedList;

public class PrintBST<Key extends Comparable<Key>, Value> {
    private Node root;  /* 根节点 */
    private int N;      /* 节点数 */
    private class Node {
        Key key;        /* 键 */
        Value val;      /* 值 */
        Node left;      /* 左子树 */
        Node right;     /* 右子树 */
        Node(Key key, Value val) {
            this.key = key;
            this.val = val;
        }
    }

    public void put(Key key, Value val) {
        root  = put(root, key, val);
        N++;
    }

    private Node put(Node x, Key key, Value val) {
        if (x == null) {
            return new Node(key, val);
        }

        int cmp = key.compareTo(x.key);
        if (cmp < 0) {
            x.left = put(x.left, key, val);
        } else if (cmp > 0) {
            x.right = put(x.right, key, val);
        } else {
            x.val = val;
        }

        return x;
    }

    public int height(Node x) {
        if (x == null)
            return 0;
        int lh = height(x.left);
        int rh = height(x.right);

        return (lh > rh) ? (lh + 1) : (rh + 1);
    }

    /* 使用队列将每个节点按一定的顺序入队出队，遍历队列中的元素即可 */
    public void printBST(Node x) {
        if (x == null)
            return;

        LinkedList<Node> lln = new LinkedList<Node>();
        lln.add(x);
        while (!lln.isEmpty()) {
            Node first  = lln.getFirst();
            System.out.println(first.key);
            if (first.left != null) {
                lln.add(first.left);
            }
            if (first.right != null) {
                lln.add(first.right);
            }
            lln.remove();
        }
    }

    public static void main(String[] args) {
        PrintBST<String, Integer> pbst = new PrintBST<String, Integer>();
        pbst.put("DDDD", 4);
        pbst.put("CCC", 3);
        pbst.put("A", 1);
        pbst.put("BB", 2);
        pbst.put("FFFFFF", 6);
        pbst.put("EEEEE", 5);

        pbst.printBST(pbst.root);
    }
}