蛇形打印二叉树

package 树;
import java.util.ArrayList;
import java.util.Deque;
import java.util.LinkedList;
//蛇形打印二叉树
public class Printerzigzag {
	public static void main(String[] args) {
		treeNode root=new treeNode(1);
		root.left=new treeNode(2);
		root.right=new treeNode(3);
		root.left.left=new treeNode(4);
		root.left.right=new treeNode(5);
		root.right.left=new treeNode(6);
		root.right.right=new treeNode(7);
		ArrayList<ArrayList<Integer>> arr=print(root);
		System.out.println();
		for(int i=0;i<arr.size();i++){
			for(int j=0;j<arr.get(i).size();j++){
				System.out.print(arr.get(i).get(j)+" ");
			}
			System.out.println();
		}
	}
	public static ArrayList<ArrayList<Integer>> print(treeNode root){
		ArrayList<Integer> array=new ArrayList<Integer>();
		ArrayList<ArrayList<Integer> > array1=new ArrayList<ArrayList<Integer> >();
		if(root==null) return array1;
		Deque<treeNode> queue=new LinkedList<treeNode>();
		queue.addLast(root);
		boolean res=true;	//标记判断从哪段进出		
		treeNode last=root; //当前行最右结点
		treeNode nlast=null;//下一行打印结果的最右结点
		treeNode p=null;
		while(!queue.isEmpty()){
			if(res==true){
				p=queue.pollFirst();	//出队
				array.add(p.val);		//加入到数组	
				if(p.left!=null){
					nlast=nlast==null?p.left:nlast;//修改nlast
					queue.addLast(p.left);
				}
				if(p.right!=null){
					nlast=nlast==null?p.right:nlast;
					queue.addLast(p.right);
				}
			}else{
				p=queue.pollLast();
				array.add(p.val);
				if(p.right!=null){
					nlast=nlast==null?p.right:nlast;
					queue.addFirst(p.right);
				}
				if(p.left!=null){
					nlast=nlast==null?p.left:nlast;
					queue.addFirst(p.left);
				}
			}
			if(last==p&&!queue.isEmpty()){//换行
				res=!res;
				last=nlast;
				nlast=null;				
				array1.add(array);
				array=new ArrayList<Integer>();
			}			
		}
		array1.add(array);//最后一组加入结果数组
		return array1;
	}
}