树-层次遍历

package com.charles.algorithm;

import java.util.LinkedList;
import java.util.Queue;

public class Tree {

    private Queue<TreeNode> elements = new LinkedList<TreeNode>();

    public static void main(String[] args) {
        /*
         * @desc: construct a tree:
         *                 root
         *             A            B
         *          C      D     E     F
         *        G   H  I  J
         */

        TreeNode root = new TreeNode("root");

        TreeNode A = new TreeNode("A");
        TreeNode B = new TreeNode("B");
        TreeNode C = new TreeNode("C");
        TreeNode D = new TreeNode("D");
        TreeNode E = new TreeNode("E");
        TreeNode F = new TreeNode("F");
        TreeNode G = new TreeNode("G");
        TreeNode H = new TreeNode("H");
        TreeNode I = new TreeNode("I");
        TreeNode J = new TreeNode("J");

        root.setLeft(A);
        root.setRight(B);
        A.setLeft(C);
        A.setRight(D);
        B.setLeft(E);
        B.setRight(F);
        C.setLeft(G);
        C.setRight(H);
        D.setLeft(I);
        D.setRight(J);

        Tree tree = new Tree();
        tree.broadTraval(root);
    }

    public void broadTraval(TreeNode root) {

        if (null != root) {
            elements.add(root);
        } else {
            return;
        }

        while (0 < elements.size()) {
            root = elements.poll();
            System.out.println(root.getData());
            if (null != root.getLeft()) {
                elements.add(root.getLeft());
            }
            if (null != root.getRight()) {
                elements.add(root.getRight());
            }
        }
    }
}

class TreeNode {
    /*
     * @Desc: define a tree node
     */

    private String data;
    private TreeNode left;
    private TreeNode right;

    public TreeNode() {
    }

    public TreeNode(String data) {
        super();
        this.data = data;
    }

    public String getData() {
        return data;
    }

    public void setData(String data) {
        this.data = data;
    }

    public TreeNode getLeft() {
        return left;
    }

    public void setLeft(TreeNode left) {
        this.left = left;
    }

    public TreeNode getRight() {
        return right;
    }

    public void setRight(TreeNode right) {
        this.right = right;
    }
}