树的深度优先遍历，广度优先遍历

package com.lkr.dataStructure;

//import javax.swing.tree.TreeNode;
import java.util.ArrayDeque;
//import com.lkr.dataStructure.TreeNode;

public class TreeBianli {

    public static void main(String[] args){
        TreeNode root = new TreeNode(1);
        TreeNode secondNode = new TreeNode(2);
        TreeNode thirdNode = new TreeNode(3);
        TreeNode forthNode = new TreeNode(4);
        TreeNode fifthNode = new TreeNode(5);
        TreeNode sixthNode = new TreeNode(6);
        TreeNode seventhNode = new TreeNode(7);
        root.right = secondNode;
        root.left = thirdNode;
        secondNode.right = forthNode;
        secondNode.left = fifthNode;
        thirdNode.right = sixthNode;
        sixthNode.left = seventhNode;

        System.out.println("深度优先遍历结果： ");
        new TreeBianli().depthOrderTraversal(root);

        System.out.println("广度优先遍历结果： ");
        new TreeBianli().levelOrderTraversal(root);

    }
    //深度优先算法采用栈来实现非递归算法
    public void depthOrderTraversal(TreeNode root){
        if(root==null){
            System.out.println("empty tree");
            return;
        }
        ArrayDeque<TreeNode> stack = new ArrayDeque<TreeNode>();
        stack.push(root);
        while (stack.isEmpty()==false){
            TreeNode node = stack.pop();
            System.out.print(node.value+"  ");
            if(node.right != null){
                stack.push(node.right);
            }
            if(node.left != null){
                stack.push(node.left);
            }
        }
        System.out.print("\n");
    }

    //广度优先算法利用队列来实现非递归算法
    public  void levelOrderTraversal(TreeNode root){
        if(null==root){
            System.out.println("empth tree");
            return;
        }
        ArrayDeque<TreeNode> queue = new ArrayDeque<>();
        queue.add(root);
        while(queue.isEmpty()== false){
            TreeNode node = queue.remove();
            System.out.print(node.value + "  ");
            if(null != node.left){
                queue.add(node.left);
            }
            if(null != node.right){
                queue.add(node.right);
            }
        }
        System.out.print("\n");
    }
}